Mojo C++ bindings: fix Connector teardown.

mojo/public/cpp/bindings/connector.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 120 matching lines @@
   // Watches |message_pipe_| (as well as other handles registered to be watched
   // together) synchronously.
   // This method:
   //   - returns true when |should_stop| is set to true;
   //   - return false when any error occurs, including |message_pipe_| being
   //     closed.
   bool SyncWatch(const bool* should_stop);
 
   // Whether currently the control flow is inside the sync handle watcher
   // callback.
+  // It always returns false after CloseMessagePipe()/PassMessagePipe().
   bool during_sync_handle_watcher_callback() const {
     return sync_handle_watcher_callback_count_ > 0;
   }
 
   base::SingleThreadTaskRunner* task_runner() const {
     return task_runner_.get();
   }
 
  private:
   // Callback of mojo::Watcher.
   void OnWatcherHandleReady(MojoResult result);
   // Callback of SyncHandleWatcher.
   void OnSyncHandleWatcherHandleReady(MojoResult result);
   void OnHandleReadyInternal(MojoResult result);
 
   void WaitToReadMore();
 
-  // Returns false if |this| was destroyed during message dispatch.
+  // Returns false if it is impossible to receive more messages in the future.
+  // |this| may have been destroyed in that case.
   WARN_UNUSED_RESULT bool ReadSingleMessage(MojoResult* read_result);
 
   // |this| can be destroyed during message dispatch.
   void ReadAllAvailableMessages();
 
   // If |force_pipe_reset| is true, this method replaces the existing
   // |message_pipe_| with a dummy message pipe handle (whose peer is closed).
   // If |force_async_handler| is true, |connection_error_handler_| is called
   // asynchronously.
   void HandleError(bool force_pipe_reset, bool force_async_handler);
 
   // Cancels any calls made to |waiter_|.
   void CancelWait();
 
   void EnsureSyncWatcherExists();
 
   base::Closure connection_error_handler_;
 
   ScopedMessagePipeHandle message_pipe_;
   MessageReceiver* incoming_receiver_ = nullptr;
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-  Watcher handle_watcher_;
+  std::unique_ptr<Watcher> handle_watcher_;
 
   bool error_ = false;
   bool drop_writes_ = false;
   bool enforce_errors_from_incoming_receiver_ = true;
 
   bool paused_ = false;
 
   // If sending messages is allowed from multiple threads, |lock_| is used to
   // protect modifications to |message_pipe_| and |drop_writes_|.
   std::unique_ptr<base::Lock> lock_;
 
   std::unique_ptr<SyncHandleWatcher> sync_watcher_;
   bool allow_woken_up_by_others_ = false;
   // If non-zero, currently the control flow is inside the sync handle watcher
   // callback.
   size_t sync_handle_watcher_callback_count_ = 0;
 
   base::ThreadChecker thread_checker_;
 
   base::Lock connected_lock_;
   bool connected_ = true;
 
   // Create a single weak ptr and use it everywhere, to avoid the malloc/free
   // cost of creating a new weak ptr whenever it is needed.
+  // NOTE: This weak pointer is invalidated when the message pipe is closed or
+  // transferred (i.e., when |connected_| is set to false).
   base::WeakPtr<Connector> weak_self_;
   base::WeakPtrFactory<Connector> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Connector);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_