Turn off computation of the interest rect in cc in synchronized paint mode.

cc/trees/layer_tree_host_pixeltest_masks.cc

Index: cc/trees/layer_tree_host_pixeltest_masks.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_masks.cc b/cc/trees/layer_tree_host_pixeltest_masks.cc
index 1e395ab4c633d209f8be697e9a15ed43fdf0ad21..6a1007702956fde4583d65a5cc0ec27636c6ccec 100644
--- a/cc/trees/layer_tree_host_pixeltest_masks.cc
+++ b/cc/trees/layer_tree_host_pixeltest_masks.cc
@@ -32,6 +32,8 @@ class MaskContentLayerClient : public ContentLayerClient {
   bool FillsBoundsCompletely() const override { return false; }
   size_t GetApproximateUnsharedMemoryUsage() const override { return 0; }
 
+  gfx::Rect PaintableRegion() override { return gfx::Rect(bounds_); }
+
   scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       PaintingControlSetting picture_control) override {
@@ -311,6 +313,7 @@ class CheckerContentLayerClient : public ContentLayerClient {
   ~CheckerContentLayerClient() override {}
   bool FillsBoundsCompletely() const override { return false; }
   size_t GetApproximateUnsharedMemoryUsage() const override { return 0; }
+  gfx::Rect PaintableRegion() override { return gfx::Rect(bounds_); }
   scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       PaintingControlSetting picture_control) override {
@@ -358,6 +361,7 @@ class CircleContentLayerClient : public ContentLayerClient {
   ~CircleContentLayerClient() override {}
   bool FillsBoundsCompletely() const override { return false; }
   size_t GetApproximateUnsharedMemoryUsage() const override { return 0; }
+  gfx::Rect PaintableRegion() override { return gfx::Rect(bounds_); }
   scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       PaintingControlSetting picture_control) override {