cc :: Move some tracking of layer_property_changed to main thread.

cc/proto/layer.proto

Index: cc/proto/layer.proto
diff --git a/cc/proto/layer.proto b/cc/proto/layer.proto
index 4676c4c00282bce4d1c23921c2e8b092d494a0bd..3498c196e890e42bbaa4032eec3da7055f42633a 100644
--- a/cc/proto/layer.proto
+++ b/cc/proto/layer.proto
@@ -69,7 +69,7 @@ message LayerProperties {
   optional PictureLayerProperties picture = 6;
 }
 
-// NEXT ID: 53
+// NEXT ID: 54
 message BaseLayerProperties {
   optional Point3F transform_origin = 1;
   optional uint32 background_color = 2;
@@ -83,6 +83,7 @@ message BaseLayerProperties {
   optional bool draws_content = 9;
   optional bool hide_layer_and_subtree = 10;
   optional bool has_render_surface = 11;
+  optional bool subtree_property_changed = 53;
   // TODO(nyquist): Add support for FilterOperation. See crbug.com/541321.
   // repeated FilterOperation filters = 12;
   // repeated FilterOperation background_filters = 13;