Preliminary compositor disabling patch.

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index b34948c5d6c633d5dd918996bd3f8bb767331d0f..2ba68c9c996c2a787c8ffd4370e0be7065616ec3 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -600,6 +600,8 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   // union) any update changes that have occurred on the main thread.
   update_rect_.Union(layer->update_rect());
   layer->SetUpdateRect(update_rect_);
+  overlay_update_rect_.Union(layer->overlay_update_rect());
+  layer->SetOverlayUpdateRect(overlay_update_rect_);
 
   layer->SetStackingOrderChanged(stacking_order_changed_);
   layer->SetDebugInfo(debug_info_);
@@ -612,6 +614,7 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   // Reset any state that should be cleared for the next update.
   stacking_order_changed_ = false;
   update_rect_ = gfx::Rect();
+  overlay_update_rect_ = gfx::Rect();
   needs_push_properties_ = false;
   num_dependents_need_push_properties_ = 0;
 }
@@ -748,6 +751,7 @@ void LayerImpl::ResetAllChangeTrackingForSubtree() {
   layer_property_changed_ = false;
 
   update_rect_ = gfx::Rect();
+  overlay_update_rect_ = gfx::Rect();
   damage_rect_ = gfx::RectF();
 
   if (render_surface_)
@@ -1080,6 +1084,11 @@ void LayerImpl::SetUpdateRect(const gfx::Rect& update_rect) {
   SetNeedsPushProperties();
 }
 
+void LayerImpl::SetOverlayUpdateRect(const gfx::Rect& overlay_update_rect) {
+  overlay_update_rect_ = overlay_update_rect;
+  SetNeedsPushProperties();
+}
+
 void LayerImpl::AddDamageRect(const gfx::RectF& damage_rect) {
   damage_rect_ = gfx::UnionRects(damage_rect_, damage_rect);
 }