cc: Explicitly invalidate all dropped recordings on the main thread.

cc/resources/picture_pile.h

Index: cc/resources/picture_pile.h
diff --git a/cc/resources/picture_pile.h b/cc/resources/picture_pile.h
index 86ef32f2182be11d9355614504701d6daf406ab7..b5a14d89efa777d6adb944b649f76c639c742a33 100644
--- a/cc/resources/picture_pile.h
+++ b/cc/resources/picture_pile.h
@@ -28,11 +28,14 @@ class CC_EXPORT PicturePile : public PicturePileBase {
       SkColor background_color,
       bool contents_opaque,
       bool contents_fill_bounds_completely,
+      const gfx::Rect& layer_bounds_rect,
       const gfx::Rect& visible_layer_rect,
       int frame_number,
       Picture::RecordingMode recording_mode,
       RenderingStatsInstrumentation* stats_instrumentation);
 
+  void SetEmptyBounds();
+
   void set_slow_down_raster_scale_factor(int factor) {
     slow_down_raster_scale_factor_for_debug_ = factor;
   }