Update Surface ID Terminology

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index cf52e9485b7854ab6c657e271c6c8f986002ca91..25a1d836d27fa05032ad8557d1d7c5247ca982b2 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -339,7 +339,7 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
 
   size_t num_queued_swap_promises() const { return swap_promise_list_.size(); }
 
-  void set_surface_id_namespace(uint32_t id_namespace);
+  void set_surface_client_id(uint32_t client_id);
   SurfaceSequence CreateSurfaceSequence();
 
   PropertyTrees* property_trees() { return &property_trees_; }
@@ -598,7 +598,7 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   // Set of layers that need to push properties.
   std::unordered_set<Layer*> layers_that_should_push_properties_;
 
-  uint32_t surface_id_namespace_;
+  uint32_t surface_client_id_;
   uint32_t next_surface_sequence_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);