Add support for ViewProps.NEEDS_OFFSCREEN_ALPHA_COMPOSITING to RCTView

Summary: Copied from ReactViewManager. Should provide performance improvements.

Reviewed By: ahmedre

Differential Revision: D2772832

ReactAndroid/src/main/java/com/facebook/react/flat/FlatViewGroup.java

@@ -57,6 +57,7 @@ import com.facebook.react.uimanager.ReactCompoundView;
   private int mDrawChildIndex = 0;
   private boolean mIsAttached = false;
   private boolean mIsLayoutRequested = false;
+  private boolean mNeedsOffscreenAlphaCompositing = false;
   private Drawable mHotspot;
 
   /* package */ FlatViewGroup(Context context) {
@@ -179,6 +180,22 @@ import com.facebook.react.uimanager.ReactCompoundView;
     }
   }
 
+  /**
+   * We override this to allow developers to determine whether they need offscreen alpha compositing
+   * or not. See the documentation of needsOffscreenAlphaCompositing in View.js.
+   */
+  @Override
+  public boolean hasOverlappingRendering() {
+    return mNeedsOffscreenAlphaCompositing;
+  }
+
+  /**
+   * See the documentation of needsOffscreenAlphaCompositing in View.js.
+   */
+  /* package */ void setNeedsOffscreenAlphaCompositing(boolean needsOffscreenAlphaCompositing) {
+    mNeedsOffscreenAlphaCompositing = needsOffscreenAlphaCompositing;
+  }
+
   /* package */ void setHotspot(Drawable hotspot) {
     if (mHotspot != null) {
       mHotspot.setCallback(null);

ReactAndroid/src/main/java/com/facebook/react/flat/RCTViewManager.java

@@ -90,4 +90,11 @@ import com.facebook.react.views.view.ReactDrawableHelper;
       }
     }
   }
+
+  @ReactProp(name = ViewProps.NEEDS_OFFSCREEN_ALPHA_COMPOSITING)
+  public void setNeedsOffscreenAlphaCompositing(
+      FlatViewGroup view,
+      boolean needsOffscreenAlphaCompositing) {
+    view.setNeedsOffscreenAlphaCompositing(needsOffscreenAlphaCompositing);
+  }
 }