Revert "[fuchsia] Implement NavigationPolicyThrottle for navigation b…

…locking"

This reverts commit 17bbb4d.

Reason for revert: Suspicious about compilation breakage:
https://ci.chromium.org/p/chromium/builders/ci/fuchsia-x64-dbg/14892

Original change's description:
> [fuchsia] Implement NavigationPolicyThrottle for navigation blocking
>
> * Add an implementation of NavigationPolicyThrottle to WebEngine
> * Add NavigationPolicyHandler, which keeps track of throttles and checks
>   if navigations need to be passed on to the client
> * Add a FakeNavigationPolicyProvider for tests
>
> Test: NavigationPolicyThrottleTest
> Bug: 1117601
> Change-Id: I0bdf94345b10d829bea4aeb85f74204970a97239
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519039
> Commit-Queue: Sharon Yang <[email protected]>
> Reviewed-by: Sergey Ulanov <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#826625}

[email protected],[email protected]

Change-Id: I5ad8cdcd55e3718a25e3fe0cb332d6d7b90b4532
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1117601
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532022
Reviewed-by: Yuki Shiino <[email protected]>
Commit-Queue: Yuki Shiino <[email protected]>
Cr-Commit-Position: refs/heads/master@{#826658}

fuchsia/engine/BUILD.gn

@@ -157,10 +157,6 @@ component("web_engine_core") {
     "browser/media_resource_provider_service.h",
     "browser/navigation_controller_impl.cc",
     "browser/navigation_controller_impl.h",
-    "browser/navigation_policy_handler.cc",
-    "browser/navigation_policy_handler.h",
-    "browser/navigation_policy_throttle.cc",
-    "browser/navigation_policy_throttle.h",
     "browser/url_request_rewrite_rules_manager.cc",
     "browser/url_request_rewrite_rules_manager.h",
     "browser/web_engine_browser_context.cc",
@@ -333,11 +329,8 @@ test("web_engine_unittests") {
     "browser/ax_tree_converter_unittest.cc",
     "browser/cookie_manager_impl_unittest.cc",
     "browser/event_filter_unittest.cc",
-    "browser/fake_navigation_policy_provider.cc",
-    "browser/fake_navigation_policy_provider.h",
     "browser/frame_impl_unittest.cc",
     "browser/media_player_impl_unittest.cc",
-    "browser/navigation_policy_throttle_unittest.cc",
     "browser/url_request_rewrite_rules_manager_unittest.cc",
     "common/web_engine_url_loader_throttle_unittest.cc",
     "context_provider_impl_unittest.cc",
@@ -350,7 +343,6 @@ test("web_engine_unittests") {
     ":switches",
     ":web_engine_core",
     "//base/test:test_support",
-    "//content/test:test_support",
     "//fuchsia/base:test_support",
     "//mojo/core/embedder",
     "//services/media_session/public/mojom",