Implement throttling behavior for LocalStorage mojo messages.

mojo/public/cpp/bindings/interface_ptr.h

Index: mojo/public/cpp/bindings/interface_ptr.h
diff --git a/mojo/public/cpp/bindings/interface_ptr.h b/mojo/public/cpp/bindings/interface_ptr.h
index a86761106e2b00bec1712cf9d0a4e941001f9676..0a710612c6a7b11e7bab7ae2bbc386e5e51c119c 100644
--- a/mojo/public/cpp/bindings/interface_ptr.h
+++ b/mojo/public/cpp/bindings/interface_ptr.h
@@ -200,6 +200,14 @@ class InterfacePtr {
     return !(*this) && !other;
   }
 
+  size_t pending_callback_count() const {
+    return internal_state_.pending_callback_count();
+  }
+
+  void set_process_async_during_sync(bool value) {
+    internal_state_.set_process_async_during_sync(value);
+  }
+
   // DO NOT USE. Exposed only for internal use and for testing.
   internal::InterfacePtrState<Interface>* internal_state() {
     return &internal_state_;