Do full layer recording in slimming paint mode

cc/resources/display_list_recording_source.cc

Index: cc/resources/display_list_recording_source.cc
diff --git a/cc/resources/display_list_recording_source.cc b/cc/resources/display_list_recording_source.cc
index a3c3d477f222cb39a7bacad7f0b3c2b6b7d2a8e1..131fbc913ee75474b467243e30a4423682409ca3 100644
--- a/cc/resources/display_list_recording_source.cc
+++ b/cc/resources/display_list_recording_source.cc
@@ -60,9 +60,10 @@ bool DisplayListRecordingSource::UpdateAndExpandInvalidation(
   }
 
   gfx::Rect old_recorded_viewport = recorded_viewport_;
-  recorded_viewport_ = visible_layer_rect;
-  recorded_viewport_.Inset(-pixel_record_distance_, -pixel_record_distance_);
-  recorded_viewport_.Intersect(gfx::Rect(GetSize()));
+  // TODO(wangxianzhu): Blink slimming paint doesn't support incremental
+  // painting for now so we must record for the whole layer. Should measure
+  // performance and determine the best choice. Consider display item caching.
+  recorded_viewport_ = gfx::Rect(GetSize());
 
   if (recorded_viewport_ != old_recorded_viewport) {
     // Invalidate newly-exposed and no-longer-exposed areas.