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

cc/layers/picture_layer.cc

Index: cc/layers/picture_layer.cc
diff --git a/cc/layers/picture_layer.cc b/cc/layers/picture_layer.cc
index 0b92ff4a9d8a432eecfe8b6fa7335a24a0ddcb4e..4387ad05d81be21cd1609accdbcbed5097da0196 100644
--- a/cc/layers/picture_layer.cc
+++ b/cc/layers/picture_layer.cc
@@ -132,11 +132,14 @@ bool PictureLayer::Update() {
   devtools_instrumentation::ScopedLayerTreeTask update_layer(
       devtools_instrumentation::kUpdateLayer, id(), layer_tree_host()->id());
 
-  // Calling paint in WebKit can sometimes cause invalidations, so save
+  // Calling paint in Blink can sometimes cause invalidations, so save
   // off the invalidation prior to calling update.
+  // TODO(chrishtr): Blink should no longer be invalidating during paint.
+  // Try to remove this code.
   pending_invalidation_.Swap(&recording_invalidation_);
   pending_invalidation_.Clear();
 
+  // TODO(chrishtr): implement this for synchronized paint.
   if (layer_tree_host()->settings().record_full_layer) {
     // Workaround for http://crbug.com/235910 - to retain backwards compat
     // the full page content must always be provided in the picture layer.