Implement throttling behavior for LocalStorage mojo messages.

mojo/public/cpp/bindings/lib/interface_ptr_state.h

Index: mojo/public/cpp/bindings/lib/interface_ptr_state.h
diff --git a/mojo/public/cpp/bindings/lib/interface_ptr_state.h b/mojo/public/cpp/bindings/lib/interface_ptr_state.h
index f4c63d2f022291ec748b1602c0a07fc46354c9bb..bb9113ba3c56fa3b22e94672aea8e4abfb75cdad 100644
--- a/mojo/public/cpp/bindings/lib/interface_ptr_state.h
+++ b/mojo/public/cpp/bindings/lib/interface_ptr_state.h
@@ -149,6 +149,10 @@ class InterfacePtrState {
     return endpoint_client_ && endpoint_client_->has_pending_responders();
   }
 
+  size_t pending_callback_count() const {
+    return endpoint_client_ ? endpoint_client_->pending_responder_count() : 0;
+  }
+
   AssociatedGroup* associated_group() {
     ConfigureProxyIfNecessary();
     return endpoint_client_->associated_group();
@@ -170,6 +174,11 @@ class InterfacePtrState {
     endpoint_client_->AcceptWithResponder(&message, responder.release());
   }
 
+  void set_process_async_during_sync(bool value) {
+    DCHECK(!router_);
+    process_async_during_sync_ = value;
+  }
+
  private:
   using Proxy = typename Interface::Proxy_;
 
@@ -190,7 +199,11 @@ class InterfacePtrState {
             : (Interface::HasSyncMethods_
                    ? MultiplexRouter::SINGLE_INTERFACE_WITH_SYNC_METHODS
                    : MultiplexRouter::SINGLE_INTERFACE);
-    router_ = new MultiplexRouter(std::move(handle_), config, true, runner_);
+    router_ = new MultiplexRouter(
+        std::move(handle_), config, true, runner_,
+        process_async_during_sync_
+            ? MultiplexRouter::ALLOW_DIRECT_CLIENT_CALLS
+            : MultiplexRouter::ALLOW_DIRECT_CLIENT_CALLS_FOR_SYNC_MESSAGES);
     router_->SetMasterInterfaceName(Interface::Name_);
     endpoint_client_.reset(new InterfaceEndpointClient(
         router_->CreateLocalEndpointHandle(kMasterInterfaceId), nullptr,
@@ -223,6 +236,8 @@ class InterfacePtrState {
 
   uint32_t version_;
 
+  bool process_async_during_sync_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(InterfacePtrState);
 };