Makes HandleWatcher block until no longer waiting on pipe

mojo/public/cpp/bindings/lib/connector.cc

Index: mojo/public/cpp/bindings/lib/connector.cc
diff --git a/mojo/public/cpp/bindings/lib/connector.cc b/mojo/public/cpp/bindings/lib/connector.cc
index 170c4d71aa30296ecef64b3efe2af494f3506955..6665ff9442a1d078d3554358215ff5a4c424cb4f 100644
--- a/mojo/public/cpp/bindings/lib/connector.cc
+++ b/mojo/public/cpp/bindings/lib/connector.cc
@@ -34,19 +34,16 @@ Connector::~Connector() {
   if (destroyed_flag_)
     *destroyed_flag_ = true;
 
-  if (async_wait_id_)
-    waiter_->CancelWait(async_wait_id_);
+  CancelWait();
 }
 
 void Connector::CloseMessagePipe() {
+  CancelWait();
   Close(message_pipe_.Pass());
 }
 
 ScopedMessagePipeHandle Connector::PassMessagePipe() {
-  if (async_wait_id_) {
-    waiter_->CancelWait(async_wait_id_);
-    async_wait_id_ = 0;
-  }
+  CancelWait();
   return message_pipe_.Pass();
 }
 
@@ -136,6 +133,7 @@ void Connector::OnHandleReady(MojoResult result) {
 }
 
 void Connector::WaitToReadMore() {
+  MOJO_DCHECK(!async_wait_id_);
   async_wait_id_ = waiter_->AsyncWait(message_pipe_.get().value(),
                                       MOJO_HANDLE_SIGNAL_READABLE,
                                       MOJO_DEADLINE_INDEFINITE,
@@ -190,6 +188,14 @@ void Connector::ReadAllAvailableMessages() {
   }
 }
 
+void Connector::CancelWait() {
+  if (!async_wait_id_)
+    return;
+
+  waiter_->CancelWait(async_wait_id_);
+  async_wait_id_ = 0;
+}
+
 void Connector::NotifyError() {
   error_ = true;
   // The error handler might destroyed |this|. Also, after an error, all method