SetNeedsRedraw directly when updating a visible tile.

cc/layers/picture_layer.h

Index: cc/layers/picture_layer.h
diff --git a/cc/layers/picture_layer.h b/cc/layers/picture_layer.h
index 232dba23ba7236c5fac6f64e46202fa63829361b..cd6bd594cc92809e4a92c6935ef2cde91c29202c 100644
--- a/cc/layers/picture_layer.h
+++ b/cc/layers/picture_layer.h
@@ -48,6 +48,9 @@ class CC_EXPORT PictureLayer : public Layer {
   bool HasDrawableContent() const override;
   void UpdateCanUseLCDText();
 
+  // A virtual method for tests to inject a custom implementation.
+  virtual scoped_refptr<PicturePileImpl> CreatePicturePileImpl();
+
  private:
   ContentLayerClient* client_;
   PicturePile pile_;