Revert Mojo-based SyncChannel waiting again

ipc/ipc_sync_channel.h

 // Copyright (c) 2012 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 IPC_IPC_SYNC_CHANNEL_H_
 #define IPC_IPC_SYNC_CHANNEL_H_
 
 #include <deque>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event_watcher.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_channel_proxy.h"
 #include "ipc/ipc_sync_message.h"
 #include "ipc/ipc_sync_message_filter.h"
-#include "mojo/public/c/system/types.h"
-#include "mojo/public/cpp/system/watcher.h"
 
 namespace base {
 class WaitableEvent;
 };
 
-namespace mojo {
-class SyncHandleRegistry;
-class Watcher;
-}
-
 namespace IPC {
 
+class SyncMessage;
 class ChannelFactory;
-class MojoEvent;
-class SyncMessage;
 
 // This is similar to ChannelProxy, with the added feature of supporting sending
 // synchronous messages.
 //
 // Overview of how the sync channel works
 // --------------------------------------
 // When the sending thread sends a synchronous message, we create a bunch
 // of tracking info (created in Send, stored in the PendingSyncMsg
 // structure) associated with the message that we identify by the unique
 // "MessageId" on the SyncMessage. Among the things we save is the
@@ skipping 89 matching lines @@
   // ChannelProxy::Context for more information.
   class SyncContext : public Context {
    public:
     SyncContext(
         Listener* listener,
         const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
         base::WaitableEvent* shutdown_event);
 
     // Adds information about an outgoing sync message to the context so that
     // we know how to deserialize the reply.
-    bool Push(SyncMessage* sync_msg);
+    void Push(SyncMessage* sync_msg);
 
     // Cleanly remove the top deserializer (and throw it away).  Returns the
     // result of the Send call for that message.
     bool Pop();
 
-    // Returns a Mojo Event that signals when a sync send is complete or timed
-    // out or the process shut down.
-    MojoEvent* GetSendDoneEvent();
+    // Returns an event that's set when the send is complete, timed out or the
+    // process shut down.
+    base::WaitableEvent* GetSendDoneEvent();
 
-    // Returns a Mojo Event that signals when an incoming message that's not the
-    // pending reply needs to get dispatched (by calling DispatchMessages.)
-    MojoEvent* GetDispatchEvent();
+    // Returns an event that's set when an incoming message that's not the reply
+    // needs to get dispatched (by calling SyncContext::DispatchMessages).
+    base::WaitableEvent* GetDispatchEvent();
 
     void DispatchMessages();
 
     // Checks if the given message is blocking the listener thread because of a
     // synchronous send.  If it is, the thread is unblocked and true is
     // returned. Otherwise the function returns false.
     bool TryToUnblockListener(const Message* msg);
 
     base::WaitableEvent* shutdown_event() { return shutdown_event_; }
 
     ReceivedSyncMsgQueue* received_sync_msgs() {
       return received_sync_msgs_.get();
     }
 
     void set_restrict_dispatch_group(int group) {
       restrict_dispatch_group_ = group;
     }
 
     int restrict_dispatch_group() const {
       return restrict_dispatch_group_;
     }
 
+    base::WaitableEventWatcher::EventCallback MakeWaitableEventCallback();
+
    private:
     ~SyncContext() override;
     // ChannelProxy methods that we override.
 
     // Called on the listener thread.
     void Clear() override;
 
     // Called on the IPC thread.
     bool OnMessageReceived(const Message& msg) override;
     void OnChannelError() override;
     void OnChannelOpened() override;
     void OnChannelClosed() override;
 
     // Cancels all pending Send calls.
     void CancelPendingSends();
 
-    void OnShutdownEventSignaled(base::WaitableEvent* event);
+    void OnWaitableEventSignaled(base::WaitableEvent* event);
 
     typedef std::deque<PendingSyncMsg> PendingSyncMessageQueue;
     PendingSyncMessageQueue deserializers_;
-    bool reject_new_deserializers_ = false;
     base::Lock deserializers_lock_;
 
     scoped_refptr<ReceivedSyncMsgQueue> received_sync_msgs_;
 
     base::WaitableEvent* shutdown_event_;
     base::WaitableEventWatcher shutdown_watcher_;
     base::WaitableEventWatcher::EventCallback shutdown_watcher_callback_;
     int restrict_dispatch_group_;
   };
 
  private:
   SyncChannel(
       Listener* listener,
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
       base::WaitableEvent* shutdown_event);
 
-  void OnDispatchHandleReady(MojoResult result);
+  void OnWaitableEventSignaled(base::WaitableEvent* arg);
 
   SyncContext* sync_context() {
     return reinterpret_cast<SyncContext*>(context());
   }
 
   // Both these functions wait for a reply, timeout or process shutdown.  The
   // latter one also runs a nested message loop in the meantime.
-  static void WaitForReply(mojo::SyncHandleRegistry* registry,
-                           SyncContext* context,
-                           bool pump_messages);
+  static void WaitForReply(
+      SyncContext* context, base::WaitableEvent* pump_messages_event);
 
   // Runs a nested message loop until a reply arrives, times out, or the process
   // shuts down.
   static void WaitForReplyWithNestedMessageLoop(SyncContext* context);
 
   // Starts the dispatch watcher.
   void StartWatching();
 
   // ChannelProxy overrides:
   void OnChannelInit() override;
 
-  scoped_refptr<mojo::SyncHandleRegistry> sync_handle_registry_;
-
   // Used to signal events between the IPC and listener threads.
-  mojo::Watcher dispatch_watcher_;
+  base::WaitableEventWatcher dispatch_watcher_;
+  base::WaitableEventWatcher::EventCallback dispatch_watcher_callback_;
 
   // Tracks SyncMessageFilters created before complete channel initialization.
   std::vector<scoped_refptr<SyncMessageFilter>> pre_init_sync_message_filters_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_CHANNEL_H_