diff --git a/flow/embedded_views.h b/flow/embedded_views.h
index 6985c37e5b8c0..c16426980f88d 100644
--- a/flow/embedded_views.h
+++ b/flow/embedded_views.h
@@ -6,6 +6,7 @@
 #define FLUTTER_FLOW_EMBEDDED_VIEWS_H_
 
 #include <memory>
+#include <utility>
 #include <vector>
 
 #include "flutter/display_list/dl_builder.h"
@@ -51,7 +52,7 @@ class ImageFilterMutation {
  public:
   ImageFilterMutation(std::shared_ptr<const DlImageFilter> filter,
                       const SkRect& filter_rect)
-      : filter_(filter), filter_rect_(filter_rect) {}
+      : filter_(std::move(filter)), filter_rect_(filter_rect) {}
 
   const DlImageFilter& GetFilter() const { return *filter_; }
   const SkRect& GetFilterRect() const { return filter_rect_; }
@@ -110,7 +111,7 @@ class Mutator {
   explicit Mutator(const SkMatrix& matrix)
       : type_(kTransform), matrix_(matrix) {}
   explicit Mutator(const int& alpha) : type_(kOpacity), alpha_(alpha) {}
-  explicit Mutator(std::shared_ptr<const DlImageFilter> filter,
+  explicit Mutator(const std::shared_ptr<const DlImageFilter>& filter,
                    const SkRect& filter_rect)
       : type_(kBackdropFilter),
         filter_mutation_(
@@ -270,7 +271,7 @@ class EmbeddedViewParams {
                      MutatorsStack mutators_stack)
       : matrix_(matrix),
         size_points_(size_points),
-        mutators_stack_(mutators_stack) {
+        mutators_stack_(std::move(mutators_stack)) {
     SkPath path;
     SkRect starting_rect = SkRect::MakeSize(size_points);
     path.addRect(starting_rect);
@@ -295,7 +296,7 @@ class EmbeddedViewParams {
   // Pushes the stored DlImageFilter object to the mutators stack.
   //
   // `filter_rect` is in global coordinates.
-  void PushImageFilter(std::shared_ptr<const DlImageFilter> filter,
+  void PushImageFilter(const std::shared_ptr<const DlImageFilter>& filter,
                        const SkRect& filter_rect) {
     mutators_stack_.PushBackdropFilter(filter, filter_rect);
   }
@@ -344,7 +345,7 @@ class EmbedderViewSlice {
 
 class DisplayListEmbedderViewSlice : public EmbedderViewSlice {
  public:
-  DisplayListEmbedderViewSlice(SkRect view_bounds);
+  explicit DisplayListEmbedderViewSlice(SkRect view_bounds);
   ~DisplayListEmbedderViewSlice() override = default;
 
   DlCanvas* canvas() override;
@@ -391,7 +392,7 @@ class ExternalViewEmbedder {
       SkISize frame_size,
       GrDirectContext* context,
       double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) = 0;
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) = 0;
 
   virtual void PrerollCompositeEmbeddedView(
       int64_t view_id,
@@ -402,7 +403,7 @@ class ExternalViewEmbedder {
   // after it does any requisite tasks needed to bring itself to a valid state.
   // Returns kSuccess if the view embedder is already in a valid state.
   virtual PostPrerollResult PostPrerollAction(
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
     return PostPrerollResult::kSuccess;
   }
 
@@ -432,7 +433,7 @@ class ExternalViewEmbedder {
   // returns false.
   virtual void EndFrame(
       bool should_resubmit_frame,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {}
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {}
 
   // Whether the embedder should support dynamic thread merging.
   //
@@ -468,7 +469,7 @@ class ExternalViewEmbedder {
   // See also: |PushVisitedPlatformView| for pushing platform view ids to the
   // visited platform views list.
   virtual void PushFilterToVisitedPlatformViews(
-      std::shared_ptr<const DlImageFilter> filter,
+      const std::shared_ptr<const DlImageFilter>& filter,
       const SkRect& filter_rect) {}
 
  private:
diff --git a/flow/testing/mock_embedder.cc b/flow/testing/mock_embedder.cc
index ae41675b6f771..1f86912fdc549 100644
--- a/flow/testing/mock_embedder.cc
+++ b/flow/testing/mock_embedder.cc
@@ -28,7 +28,7 @@ void MockViewEmbedder::BeginFrame(
     SkISize frame_size,
     GrDirectContext* context,
     double device_pixel_ratio,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {}
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {}
 
 // |ExternalViewEmbedder|
 void MockViewEmbedder::PrerollCompositeEmbeddedView(
diff --git a/flow/testing/mock_embedder.h b/flow/testing/mock_embedder.h
index 164d7baff79e3..5ea8fdf8a7cbc 100644
--- a/flow/testing/mock_embedder.h
+++ b/flow/testing/mock_embedder.h
@@ -25,11 +25,11 @@ class MockViewEmbedder : public ExternalViewEmbedder {
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(
diff --git a/shell/common/rasterizer_unittests.cc b/shell/common/rasterizer_unittests.cc
index 1e21d0d8f1ecb..10085e66ade0e 100644
--- a/shell/common/rasterizer_unittests.cc
+++ b/shell/common/rasterizer_unittests.cc
@@ -89,21 +89,23 @@ class MockExternalViewEmbedder : public ExternalViewEmbedder {
  public:
   MOCK_METHOD(DlCanvas*, GetRootCanvas, (), (override));
   MOCK_METHOD(void, CancelFrame, (), (override));
-  MOCK_METHOD(void,
-              BeginFrame,
-              (SkISize frame_size,
-               GrDirectContext* context,
-               double device_pixel_ratio,
-               fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger),
-              (override));
+  MOCK_METHOD(
+      void,
+      BeginFrame,
+      (SkISize frame_size,
+       GrDirectContext* context,
+       double device_pixel_ratio,
+       const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger),
+      (override));
   MOCK_METHOD(void,
               PrerollCompositeEmbeddedView,
               (int64_t view_id, std::unique_ptr<EmbeddedViewParams> params),
               (override));
-  MOCK_METHOD(PostPrerollResult,
-              PostPrerollAction,
-              (fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger),
-              (override));
+  MOCK_METHOD(
+      PostPrerollResult,
+      PostPrerollAction,
+      (const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger),
+      (override));
   MOCK_METHOD(DlCanvas*, CompositeEmbeddedView, (int64_t view_id), (override));
   MOCK_METHOD(void,
               SubmitFrame,
@@ -111,11 +113,12 @@ class MockExternalViewEmbedder : public ExternalViewEmbedder {
                const std::shared_ptr<impeller::AiksContext>& aiks_context,
                std::unique_ptr<SurfaceFrame> frame),
               (override));
-  MOCK_METHOD(void,
-              EndFrame,
-              (bool should_resubmit_frame,
-               fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger),
-              (override));
+  MOCK_METHOD(
+      void,
+      EndFrame,
+      (bool should_resubmit_frame,
+       const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger),
+      (override));
   MOCK_METHOD(bool, SupportsDynamicThreadMerging, (), (override));
 };
 }  // namespace
@@ -199,7 +202,8 @@ TEST(RasterizerTest,
   framebuffer_info.supports_readback = true;
 
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, framebuffer_info,
+      /*surface=*/
+      nullptr, framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(true));
@@ -271,7 +275,8 @@ TEST(
   SurfaceFrame::FramebufferInfo framebuffer_info;
   framebuffer_info.supports_readback = true;
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, framebuffer_info,
+      /*surface=*/
+      nullptr, framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(true));
@@ -343,7 +348,8 @@ TEST(
   framebuffer_info.supports_readback = true;
 
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, framebuffer_info,
+      /*surface=*/
+      nullptr, framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(true));
@@ -412,11 +418,13 @@ TEST(RasterizerTest,
   framebuffer_info.supports_readback = true;
 
   auto surface_frame1 = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, framebuffer_info,
+      /*surface=*/
+      nullptr, framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   auto surface_frame2 = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, framebuffer_info,
+      /*surface=*/
+      nullptr, framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled())
@@ -645,7 +653,8 @@ TEST(RasterizerTest,
   SurfaceFrame::FramebufferInfo framebuffer_info;
   framebuffer_info.supports_readback = true;
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, /*framebuffer_info=*/framebuffer_info,
+      /*surface=*/
+      nullptr, /*framebuffer_info=*/framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(true));
@@ -704,7 +713,8 @@ TEST(
   framebuffer_info.supports_readback = true;
 
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, /*framebuffer_info=*/framebuffer_info,
+      /*surface=*/
+      nullptr, /*framebuffer_info=*/framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(true));
@@ -764,7 +774,8 @@ TEST(
   framebuffer_info.supports_readback = true;
 
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, /*framebuffer_info=*/framebuffer_info,
+      /*surface=*/
+      nullptr, /*framebuffer_info=*/framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(false));
@@ -823,7 +834,8 @@ TEST(
   framebuffer_info.supports_readback = true;
 
   auto surface_frame = std::make_unique<SurfaceFrame>(
-      /*surface=*/nullptr, /*framebuffer_info=*/framebuffer_info,
+      /*surface=*/
+      nullptr, /*framebuffer_info=*/framebuffer_info,
       /*submit_callback=*/[](const SurfaceFrame&, DlCanvas*) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
   EXPECT_CALL(*surface, AllowsDrawingWhenGpuDisabled()).WillOnce(Return(false));
@@ -945,7 +957,8 @@ TEST(RasterizerTest,
         SurfaceFrame::FramebufferInfo framebuffer_info;
         framebuffer_info.supports_readback = true;
         return std::make_unique<SurfaceFrame>(
-            /*surface=*/nullptr, framebuffer_info,
+            /*surface=*/
+            nullptr, framebuffer_info,
             /*submit_callback=*/
             [](const SurfaceFrame& frame, DlCanvas*) { return true; },
             /*frame_size=*/SkISize::Make(800, 600));
diff --git a/shell/common/shell_test_external_view_embedder.cc b/shell/common/shell_test_external_view_embedder.cc
index 22b9bfe13554b..6c87e734982c2 100644
--- a/shell/common/shell_test_external_view_embedder.cc
+++ b/shell/common/shell_test_external_view_embedder.cc
@@ -44,7 +44,7 @@ void ShellTestExternalViewEmbedder::BeginFrame(
     SkISize frame_size,
     GrDirectContext* context,
     double device_pixel_ratio,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   visited_platform_views_.clear();
   mutators_stacks_.clear();
   current_composition_params_.clear();
@@ -61,7 +61,7 @@ void ShellTestExternalViewEmbedder::PrerollCompositeEmbeddedView(
 
 // |ExternalViewEmbedder|
 PostPrerollResult ShellTestExternalViewEmbedder::PostPrerollAction(
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   FML_DCHECK(raster_thread_merger);
   return post_preroll_result_;
 }
@@ -73,7 +73,7 @@ void ShellTestExternalViewEmbedder::PushVisitedPlatformView(int64_t view_id) {
 
 // |ExternalViewEmbedder|
 void ShellTestExternalViewEmbedder::PushFilterToVisitedPlatformViews(
-    std::shared_ptr<const DlImageFilter> filter,
+    const std::shared_ptr<const DlImageFilter>& filter,
     const SkRect& filter_rect) {
   for (int64_t id : visited_platform_views_) {
     EmbeddedViewParams params = current_composition_params_[id];
@@ -109,7 +109,7 @@ void ShellTestExternalViewEmbedder::SubmitFrame(
 // |ExternalViewEmbedder|
 void ShellTestExternalViewEmbedder::EndFrame(
     bool should_resubmit_frame,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   end_frame_call_back_(should_resubmit_frame, raster_thread_merger);
 }
 
diff --git a/shell/common/shell_test_external_view_embedder.h b/shell/common/shell_test_external_view_embedder.h
index b2e8c48d0ccf0..93aca8578f0d3 100644
--- a/shell/common/shell_test_external_view_embedder.h
+++ b/shell/common/shell_test_external_view_embedder.h
@@ -46,11 +46,11 @@ class ShellTestExternalViewEmbedder final : public ExternalViewEmbedder {
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(
@@ -59,7 +59,8 @@ class ShellTestExternalViewEmbedder final : public ExternalViewEmbedder {
 
   // |ExternalViewEmbedder|
   PostPrerollResult PostPrerollAction(
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger)
+      override;
 
   // |ExternalViewEmbedder|
   DlCanvas* CompositeEmbeddedView(int64_t view_id) override;
@@ -69,7 +70,7 @@ class ShellTestExternalViewEmbedder final : public ExternalViewEmbedder {
 
   // |ExternalViewEmbedder|
   void PushFilterToVisitedPlatformViews(
-      std::shared_ptr<const DlImageFilter> filter,
+      const std::shared_ptr<const DlImageFilter>& filter,
       const SkRect& filter_rect) override;
 
   // |ExternalViewEmbedder|
@@ -78,9 +79,9 @@ class ShellTestExternalViewEmbedder final : public ExternalViewEmbedder {
                    std::unique_ptr<SurfaceFrame> frame) override;
 
   // |ExternalViewEmbedder|
-  void EndFrame(
-      bool should_resubmit_frame,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void EndFrame(bool should_resubmit_frame,
+                const fml::RefPtr<fml::RasterThreadMerger>&
+                    raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   DlCanvas* GetRootCanvas() override;
diff --git a/shell/platform/android/external_view_embedder/external_view_embedder.cc b/shell/platform/android/external_view_embedder/external_view_embedder.cc
index a0e516e4c10a2..905c2751a3d4b 100644
--- a/shell/platform/android/external_view_embedder/external_view_embedder.cc
+++ b/shell/platform/android/external_view_embedder/external_view_embedder.cc
@@ -212,7 +212,7 @@ AndroidExternalViewEmbedder::CreateSurfaceIfNeeded(GrDirectContext* context,
 
 // |ExternalViewEmbedder|
 PostPrerollResult AndroidExternalViewEmbedder::PostPrerollAction(
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   if (!FrameHasPlatformLayers()) {
     return PostPrerollResult::kSuccess;
   }
@@ -260,7 +260,7 @@ void AndroidExternalViewEmbedder::BeginFrame(
     SkISize frame_size,
     GrDirectContext* context,
     double device_pixel_ratio,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   Reset();
 
   // The surface size changed. Therefore, destroy existing surfaces as
@@ -286,7 +286,7 @@ void AndroidExternalViewEmbedder::CancelFrame() {
 // |ExternalViewEmbedder|
 void AndroidExternalViewEmbedder::EndFrame(
     bool should_resubmit_frame,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   surface_pool_->RecycleLayers();
   // JNI method must be called on the platform thread.
   if (raster_thread_merger->IsOnPlatformThread()) {
diff --git a/shell/platform/android/external_view_embedder/external_view_embedder.h b/shell/platform/android/external_view_embedder/external_view_embedder.h
index 400b43fb91a89..a84681ab098d5 100644
--- a/shell/platform/android/external_view_embedder/external_view_embedder.h
+++ b/shell/platform/android/external_view_embedder/external_view_embedder.h
@@ -49,25 +49,26 @@ class AndroidExternalViewEmbedder final : public ExternalViewEmbedder {
 
   // |ExternalViewEmbedder|
   PostPrerollResult PostPrerollAction(
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger)
+      override;
 
   // |ExternalViewEmbedder|
   DlCanvas* GetRootCanvas() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void EndFrame(
-      bool should_resubmit_frame,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void EndFrame(bool should_resubmit_frame,
+                const fml::RefPtr<fml::RasterThreadMerger>&
+                    raster_thread_merger) override;
 
   bool SupportsDynamicThreadMerging() override;
 
diff --git a/shell/platform/darwin/ios/ios_external_view_embedder.h b/shell/platform/darwin/ios/ios_external_view_embedder.h
index d83b435930f21..1aa67890d6117 100644
--- a/shell/platform/darwin/ios/ios_external_view_embedder.h
+++ b/shell/platform/darwin/ios/ios_external_view_embedder.h
@@ -31,11 +31,11 @@ class IOSExternalViewEmbedder : public ExternalViewEmbedder {
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(
@@ -44,7 +44,8 @@ class IOSExternalViewEmbedder : public ExternalViewEmbedder {
 
   // |ExternalViewEmbedder|
   PostPrerollResult PostPrerollAction(
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger)
+      override;
 
   // |ExternalViewEmbedder|
   DlCanvas* CompositeEmbeddedView(int64_t view_id) override;
@@ -55,16 +56,16 @@ class IOSExternalViewEmbedder : public ExternalViewEmbedder {
                    std::unique_ptr<SurfaceFrame> frame) override;
 
   // |ExternalViewEmbedder|
-  void EndFrame(
-      bool should_resubmit_frame,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void EndFrame(bool should_resubmit_frame,
+                const fml::RefPtr<fml::RasterThreadMerger>&
+                    raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   bool SupportsDynamicThreadMerging() override;
 
   // |ExternalViewEmbedder|
   void PushFilterToVisitedPlatformViews(
-      std::shared_ptr<const DlImageFilter> filter,
+      const std::shared_ptr<const DlImageFilter>& filter,
       const SkRect& filter_rect) override;
 
   // |ExternalViewEmbedder|
diff --git a/shell/platform/darwin/ios/ios_external_view_embedder.mm b/shell/platform/darwin/ios/ios_external_view_embedder.mm
index 67112e999d13d..3f4edffdd8c6f 100644
--- a/shell/platform/darwin/ios/ios_external_view_embedder.mm
+++ b/shell/platform/darwin/ios/ios_external_view_embedder.mm
@@ -34,7 +34,7 @@
     SkISize frame_size,
     GrDirectContext* context,
     double device_pixel_ratio,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   TRACE_EVENT0("flutter", "IOSExternalViewEmbedder::BeginFrame");
   FML_CHECK(platform_views_controller_);
   platform_views_controller_->BeginFrame(frame_size);
@@ -51,7 +51,7 @@
 
 // |ExternalViewEmbedder|
 PostPrerollResult IOSExternalViewEmbedder::PostPrerollAction(
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   TRACE_EVENT0("flutter", "IOSExternalViewEmbedder::PostPrerollAction");
   FML_CHECK(platform_views_controller_);
   PostPrerollResult result = platform_views_controller_->PostPrerollAction(raster_thread_merger);
@@ -77,8 +77,9 @@
 }
 
 // |ExternalViewEmbedder|
-void IOSExternalViewEmbedder::EndFrame(bool should_resubmit_frame,
-                                       fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+void IOSExternalViewEmbedder::EndFrame(
+    bool should_resubmit_frame,
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   TRACE_EVENT0("flutter", "IOSExternalViewEmbedder::EndFrame");
   platform_views_controller_->EndFrame(should_resubmit_frame, raster_thread_merger);
 }
@@ -90,7 +91,7 @@
 
 // |ExternalViewEmbedder|
 void IOSExternalViewEmbedder::PushFilterToVisitedPlatformViews(
-    std::shared_ptr<const DlImageFilter> filter,
+    const std::shared_ptr<const DlImageFilter>& filter,
     const SkRect& filter_rect) {
   platform_views_controller_->PushFilterToVisitedPlatformViews(filter, filter_rect);
 }
diff --git a/shell/platform/embedder/embedder_external_view_embedder.cc b/shell/platform/embedder/embedder_external_view_embedder.cc
index ca38e86af4826..94c770f809277 100644
--- a/shell/platform/embedder/embedder_external_view_embedder.cc
+++ b/shell/platform/embedder/embedder_external_view_embedder.cc
@@ -54,7 +54,7 @@ void EmbedderExternalViewEmbedder::BeginFrame(
     SkISize frame_size,
     GrDirectContext* context,
     double device_pixel_ratio,
-    fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
+    const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger) {
   Reset();
 
   pending_frame_size_ = frame_size;
diff --git a/shell/platform/embedder/embedder_external_view_embedder.h b/shell/platform/embedder/embedder_external_view_embedder.h
index 014f7393c416e..31b1f4cf6f22b 100644
--- a/shell/platform/embedder/embedder_external_view_embedder.h
+++ b/shell/platform/embedder/embedder_external_view_embedder.h
@@ -81,11 +81,11 @@ class EmbedderExternalViewEmbedder final : public ExternalViewEmbedder {
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(
diff --git a/shell/platform/fuchsia/flutter/external_view_embedder.h b/shell/platform/fuchsia/flutter/external_view_embedder.h
index a5771a9ce4bfc..4e5afd151ba86 100644
--- a/shell/platform/fuchsia/flutter/external_view_embedder.h
+++ b/shell/platform/fuchsia/flutter/external_view_embedder.h
@@ -68,19 +68,20 @@ class ExternalViewEmbedder final : public flutter::ExternalViewEmbedder {
 
   // |ExternalViewEmbedder|
   flutter::PostPrerollResult PostPrerollAction(
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+      const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger)
+      override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
-  void EndFrame(
-      bool should_resubmit_frame,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;
+  void EndFrame(bool should_resubmit_frame,
+                const fml::RefPtr<fml::RasterThreadMerger>&
+                    raster_thread_merger) override;
 
   // |ExternalViewEmbedder|
   void SubmitFrame(GrDirectContext* context,
diff --git a/shell/platform/fuchsia/flutter/tests/platform_view_unittest.cc b/shell/platform/fuchsia/flutter/tests/platform_view_unittest.cc
index f19c04ba56bc2..274818de22669 100644
--- a/shell/platform/fuchsia/flutter/tests/platform_view_unittest.cc
+++ b/shell/platform/fuchsia/flutter/tests/platform_view_unittest.cc
@@ -45,11 +45,11 @@ class MockExternalViewEmbedder : public flutter::ExternalViewEmbedder {
   flutter::DlCanvas* GetRootCanvas() override { return nullptr; }
 
   void CancelFrame() override {}
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override {}
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override {}
 
   void SubmitFrame(GrDirectContext* context,
                    const std::shared_ptr<impeller::AiksContext>& aiks_context,
diff --git a/shell/testing/tester_main.cc b/shell/testing/tester_main.cc
index 4be39c4d70b41..a621dc86acf67 100644
--- a/shell/testing/tester_main.cc
+++ b/shell/testing/tester_main.cc
@@ -138,11 +138,11 @@ class TesterExternalViewEmbedder : public ExternalViewEmbedder {
   void CancelFrame() override {}
 
   // |ExternalViewEmbedder|
-  void BeginFrame(
-      SkISize frame_size,
-      GrDirectContext* context,
-      double device_pixel_ratio,
-      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override {}
+  void BeginFrame(SkISize frame_size,
+                  GrDirectContext* context,
+                  double device_pixel_ratio,
+                  const fml::RefPtr<fml::RasterThreadMerger>&
+                      raster_thread_merger) override {}
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(