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/AbstractClippingDrawCommand.java

@@ -62,8 +62,6 @@ import android.graphics.Canvas;
     // shows up during screenshot testing. Note that checking one side is enough, since if one side
     // is infinite, all sides will be infinite, since we only set infinite for all sides at the
     // same time - conversely, if one side is finite, all sides will be finite.
-    if (mNeedsClipping) {
-      canvas.clipRect(mClipLeft, mClipTop, mClipRight, mClipBottom);
-    }
+    canvas.clipRect(mClipLeft, mClipTop, mClipRight, mClipBottom);
   }
 }

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

@@ -31,7 +31,7 @@ import android.graphics.Canvas;
   public final void draw(FlatViewGroup parent, Canvas canvas) {
     onPreDraw(parent, canvas);
     if (shouldClip()) {
-      canvas.save();
+      canvas.save(Canvas.CLIP_SAVE_FLAG);
       applyClipping(canvas);
       onDraw(canvas);
       canvas.restore();

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();

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

@@ -346,7 +346,7 @@ import com.facebook.react.views.image.ImageLoadEvent;
       super.drawChild(canvas, child, getDrawingTime());
     } else {
       // Make sure non-React Views clip properly.
-      canvas.save();
+      canvas.save(Canvas.CLIP_SAVE_FLAG);
       child.getHitRect(VIEW_BOUNDS);
       canvas.clipRect(VIEW_BOUNDS);
       super.drawChild(canvas, child, getDrawingTime());