Enable partial recording if slimmingPaintDisplayItemCache is enabled

cc/resources/display_list_recording_source.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/resources/display_list_recording_source.h"
 
 #include <algorithm>
 
 #include "cc/base/region.h"
 #include "cc/layers/content_layer_client.h"
@@ skipping 42 matching lines @@
     updated = true;
   }
 
   if (can_use_lcd_text_ != can_use_lcd_text) {
     can_use_lcd_text_ = can_use_lcd_text;
     invalidation->Union(gfx::Rect(GetSize()));
     updated = true;
   }
 
   gfx::Rect old_recorded_viewport = recorded_viewport_;
-  // 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());
+  recorded_viewport_ = visible_layer_rect;
+  recorded_viewport_.Inset(-pixel_record_distance_, -pixel_record_distance_);
+  recorded_viewport_.Intersect(gfx::Rect(GetSize()));
 
   if (recorded_viewport_ != old_recorded_viewport) {
     // Invalidate newly-exposed and no-longer-exposed areas.
     Region newly_exposed_region(recorded_viewport_);
     newly_exposed_region.Subtract(old_recorded_viewport);
     invalidation->Union(newly_exposed_region);
 
     Region no_longer_exposed_region(old_recorded_viewport);
     no_longer_exposed_region.Subtract(recorded_viewport_);
     invalidation->Union(no_longer_exposed_region);
@@ skipping 90 matching lines @@
   is_solid_color_ = canvas.GetColorIfSolid(&solid_color_);
 }
 
 void DisplayListRecordingSource::Clear() {
   recorded_viewport_ = gfx::Rect();
   display_list_ = NULL;
   is_solid_color_ = false;
 }
 
 }  // namespace cc