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

cc/trees/layer_tree_host_pixeltest_tiles.cc

Index: cc/trees/layer_tree_host_pixeltest_tiles.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_tiles.cc b/cc/trees/layer_tree_host_pixeltest_tiles.cc
index 932972100da82760d69113ce9cafc25919c4d78d..f9b28aae92488b8a47cd69ded2fb887614b14829 100644
--- a/cc/trees/layer_tree_host_pixeltest_tiles.cc
+++ b/cc/trees/layer_tree_host_pixeltest_tiles.cc
@@ -105,6 +105,7 @@ class BlueYellowClient : public ContentLayerClient {
   explicit BlueYellowClient(const gfx::Size& size)
       : size_(size), blue_top_(true) {}
 
+  gfx::Rect PaintableRegion() override { return gfx::Rect(size_); }
   scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       PaintingControlSetting painting_status) override {