Don't save matrix when using canvas.save

Summary:
Canvas.save by default saves both the matrix (for translations,
scaling, etc) and the clip (clipRect) - in most of our cases, we really only
care to save and restore the clip, not the matrix.

Reviewed By: sriramramani

Differential Revision: D3235698

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

@@ -22,7 +22,7 @@ import android.graphics.Canvas;
   @Override
   public void draw(FlatViewGroup parent, Canvas canvas) {
     if (mNeedsClipping) {
-      canvas.save();
+      canvas.save(Canvas.CLIP_SAVE_FLAG);
       applyClipping(canvas);
       parent.drawNextChild(canvas);
       canvas.restore();