add flag to test running BG UI operation on a separate thread from th…

…e native modules thread

Reviewed By: achen1

Differential Revision: D4912045

fbshipit-source-id: b0b1aea24f8d463b95369636b7df2422a23aab22

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java

@@ -152,6 +152,7 @@ public interface ReactInstanceEventListener {
   private final boolean mLazyNativeModulesEnabled;
   private final boolean mLazyViewManagersEnabled;
   private final boolean mSetupReactContextInBackgroundEnabled;
+  private final boolean mUseSeparateUIBackgroundThread;
 
   private final ReactInstanceDevCommandsHandler mDevInterface =
       new ReactInstanceDevCommandsHandler() {
@@ -223,7 +224,8 @@ public static ReactInstanceManagerBuilder builder() {
     @Nullable RedBoxHandler redBoxHandler,
     boolean lazyNativeModulesEnabled,
     boolean lazyViewManagersEnabled,
-    boolean setupReactContextInBackgroundEnabled) {
+    boolean setupReactContextInBackgroundEnabled,
+    boolean useSeparateUIBackgroundThread) {
 
     initializeSoLoaderIfNecessary(applicationContext);
 
@@ -253,6 +255,7 @@ public static ReactInstanceManagerBuilder builder() {
     mLazyNativeModulesEnabled = lazyNativeModulesEnabled;
     mLazyViewManagersEnabled = lazyViewManagersEnabled;
     mSetupReactContextInBackgroundEnabled = setupReactContextInBackgroundEnabled;
+    mUseSeparateUIBackgroundThread = useSeparateUIBackgroundThread;
 
     // Instantiate ReactChoreographer in UI thread.
     ReactChoreographer.initialize();

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManagerBuilder.java

@@ -43,6 +43,7 @@ public class ReactInstanceManagerBuilder {
   protected boolean mLazyNativeModulesEnabled;
   protected boolean mLazyViewManagersEnabled;
   protected boolean mSetupReactContextInBackground;
+  protected boolean mUseSeparateUIBackgroundThread;
 
   /* package protected */ ReactInstanceManagerBuilder() {
   }
@@ -193,6 +194,12 @@ public ReactInstanceManagerBuilder setSetupReactContextInBackgroundEnabled(
     return this;
   }
 
+  public ReactInstanceManagerBuilder setUseSeparateUIBackgroundThread(
+    boolean useSeparateUIBackgroundThread) {
+   mUseSeparateUIBackgroundThread = useSeparateUIBackgroundThread;
+   return this;
+  }
+
   /**
    * Instantiates a new {@link ReactInstanceManager}.
    * Before calling {@code build}, the following must be called:
@@ -238,6 +245,7 @@ public ReactInstanceManager build() {
       mRedBoxHandler,
       mLazyNativeModulesEnabled,
       mLazyViewManagersEnabled,
-      mSetupReactContextInBackground);
+      mSetupReactContextInBackground,
+      mUseSeparateUIBackgroundThread);
   }
 }