Support rounded clipping

Summary:
Support rounded clipping in Nodes. Before, if a view had
a radius and had overflow of hidden, its children could still draw
outside of it (specifically, in the area between the rounded rect
and square rect) - this is due to the fact that clipping is, by
default, rectangular. This patch supports this type of rounded
clipping.

Differential Revision: D3634861

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

@@ -75,7 +75,7 @@ import android.graphics.Color;
     return mClipBottom;
   }
 
-  protected final void applyClipping(Canvas canvas) {
+  protected void applyClipping(Canvas canvas) {
     canvas.clipRect(mClipLeft, mClipTop, mClipRight, mClipBottom);
   }