Dirty rects always contain full tiles with delegated rendering.

cc/resources/skpicture_content_layer_updater.cc

Index: cc/resources/skpicture_content_layer_updater.cc
diff --git a/cc/resources/skpicture_content_layer_updater.cc b/cc/resources/skpicture_content_layer_updater.cc
index f1cf45439a70bcb5ed22ff496e116349243ae242..5dd68366af305647d60c4984a81914e3bcde3383 100644
--- a/cc/resources/skpicture_content_layer_updater.cc
+++ b/cc/resources/skpicture_content_layer_updater.cc
@@ -23,6 +23,7 @@ SkPictureContentLayerUpdater::~SkPictureContentLayerUpdater() {}
 
 void SkPictureContentLayerUpdater::PrepareToUpdate(
     gfx::Rect content_rect,
+    gfx::Rect paint_rect,
     gfx::Size,
     float contents_width_scale,
     float contents_height_scale,
@@ -33,6 +34,7 @@ void SkPictureContentLayerUpdater::PrepareToUpdate(
       rendering_stats_instrumentation_->StartRecording();
   PaintContents(canvas,
                 content_rect,
+                paint_rect,
                 contents_width_scale,
                 contents_height_scale,
                 resulting_opaque_rect);