Dirty rects always contain full tiles with delegated rendering.

cc/resources/content_layer_updater.cc

Index: cc/resources/content_layer_updater.cc
diff --git a/cc/resources/content_layer_updater.cc b/cc/resources/content_layer_updater.cc
index e3f87a4c272a08aca0278226cd83c74294c52c5c..86cb582cee791eaa9cc988d9d7efd346a93135aa 100644
--- a/cc/resources/content_layer_updater.cc
+++ b/cc/resources/content_layer_updater.cc
@@ -24,8 +24,8 @@ ContentLayerUpdater::ContentLayerUpdater(
     int layer_id)
     : rendering_stats_instrumentation_(stats_instrumentation),
       layer_id_(layer_id),
-      painter_(painter.Pass()),
-      layer_is_opaque_(false) {}
+      layer_is_opaque_(false),
+      painter_(painter.Pass()) {}
 
 ContentLayerUpdater::~ContentLayerUpdater() {}
 
@@ -36,6 +36,7 @@ void ContentLayerUpdater::set_rendering_stats_instrumentation(
 
 void ContentLayerUpdater::PaintContents(SkCanvas* canvas,
                                         gfx::Rect content_rect,
+                                        gfx::Rect paint_rect,
                                         float contents_width_scale,
                                         float contents_height_scale,
                                         gfx::Rect* resulting_opaque_rect) {
@@ -80,6 +81,7 @@ void ContentLayerUpdater::PaintContents(SkCanvas* canvas,
   *resulting_opaque_rect = opaque_content_rect;
 
   content_rect_ = content_rect;
+  paint_rect_ = paint_rect;
 }
 
 void ContentLayerUpdater::SetOpaque(bool opaque) {