Refactor: Simplify WaitableEventWatcher.

This change uses a callback instead of a delegate for specifying what
should be called when a WaitableEvent occurs.

This simplifies the class and gets rid of a workaround internal to the
class to prevent name collision on "Delegate" inner classes.

Tested (linux and windows):
  out/Debug/base_unittests --gtest_filter=*WaitableEventWatcherTest*
  out/Release/ipc_tests with valgrind and leak-check=yes

Previously reverted at:
  https://codereview.chromium.org/12087120/


BUG=


Review URL: https://chromiumcodereview.appspot.com/12094106

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180450 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 27 insertions, 15 deletions

diff --git a/ipc/ipc_sync_channel.cc b/ipc/ipc_sync_channel.cc
index a300c0f..1ce9f6c 100644
--- a/ipc/ipc_sync_channel.cc
+++ b/ipc/ipc_sync_channel.cc
@@ -353,7 +353,10 @@ void SyncChannel::SyncContext::OnChannelError() {
 }
 
 void SyncChannel::SyncContext::OnChannelOpened() {
-  shutdown_watcher_.StartWatching(shutdown_event_, this);
+  shutdown_watcher_.StartWatching(
+      shutdown_event_,
+      base::Bind(&SyncChannel::SyncContext::OnWaitableEventSignaled,
+                 base::Unretained(this)));
   Context::OnChannelOpened();
 }
 
@@ -396,6 +399,10 @@ void SyncChannel::SyncContext::OnWaitableEventSignaled(WaitableEvent* event) {
   }
 }
 
+base::WaitableEventWatcher::EventCallback
+    SyncChannel::SyncContext::MakeWaitableEventCallback() {
+  return base::Bind(&SyncChannel::SyncContext::OnWaitableEventSignaled, this);
+}
 
 SyncChannel::SyncChannel(
     const IPC::ChannelHandle& channel_handle,
@@ -517,21 +524,22 @@ void SyncChannel::WaitForReplyWithNestedMessageLoop(SyncContext* context) {
   base::WaitableEventWatcher* old_send_done_event_watcher =
       sync_msg_queue->top_send_done_watcher();
 
-  base::WaitableEventWatcher::Delegate* old_delegate = NULL;
+  base::WaitableEventWatcher::EventCallback old_callback;
   base::WaitableEvent* old_event = NULL;
 
   // Maintain a local global stack of send done delegates to ensure that
   // nested sync calls complete in the correct sequence, i.e. the
   // outermost call completes first, etc.
   if (old_send_done_event_watcher) {
-    old_delegate = old_send_done_event_watcher->delegate();
+    old_callback = old_send_done_event_watcher->callback();
     old_event = old_send_done_event_watcher->GetWatchedEvent();
     old_send_done_event_watcher->StopWatching();
   }
 
   sync_msg_queue->set_top_send_done_watcher(&send_done_watcher);
 
-  send_done_watcher.StartWatching(context->GetSendDoneEvent(), context);
+  send_done_watcher.StartWatching(context->GetSendDoneEvent(),
+                                  context->MakeWaitableEventCallback());
 
   {
     MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
@@ -540,7 +548,7 @@ void SyncChannel::WaitForReplyWithNestedMessageLoop(SyncContext* context) {
 
   sync_msg_queue->set_top_send_done_watcher(old_send_done_event_watcher);
   if (old_send_done_event_watcher && old_event) {
-    old_send_done_event_watcher->StartWatching(old_event, old_delegate);
+    old_send_done_event_watcher->StartWatching(old_event, old_callback);
   }
 }
 
@@ -549,7 +557,7 @@ void SyncChannel::OnWaitableEventSignaled(WaitableEvent* event) {
   // The call to DispatchMessages might delete this object, so reregister
   // the object watcher first.
   event->Reset();
-  dispatch_watcher_.StartWatching(event, this);
+  dispatch_watcher_.StartWatching(event, dispatch_watcher_callback_);
   sync_context()->DispatchMessages();
 }
 
@@ -560,7 +568,11 @@ void SyncChannel::StartWatching() {
   // stop or keep watching.  So we always watch it, and create the event as
   // manual reset since the object watcher might otherwise reset the event
   // when we're doing a WaitMany.
-  dispatch_watcher_.StartWatching(sync_context()->GetDispatchEvent(), this);
+  dispatch_watcher_callback_ =
+      base::Bind(&SyncChannel::OnWaitableEventSignaled,
+                  base::Unretained(this));
+  dispatch_watcher_.StartWatching(sync_context()->GetDispatchEvent(),
+                                  dispatch_watcher_callback_);
 }
 
 }  // namespace IPC
diff --git a/ipc/ipc_sync_channel.h b/ipc/ipc_sync_channel.h
index 87fc1f4..8b66432 100644
--- a/ipc/ipc_sync_channel.h
+++ b/ipc/ipc_sync_channel.h
@@ -58,8 +58,7 @@ class SyncMessage;
 // is more than this object.  If the message loop goes away while this object
 // is running and it's used to send a message, then it will use the invalid
 // message loop pointer to proxy it to the ipc thread.
-class IPC_EXPORT SyncChannel : public ChannelProxy,
-                               public base::WaitableEventWatcher::Delegate {
+class IPC_EXPORT SyncChannel : public ChannelProxy {
  public:
   enum RestrictDispatchGroup {
     kRestrictDispatchGroup_None = 0,
@@ -115,8 +114,7 @@ class IPC_EXPORT SyncChannel : public ChannelProxy,
   // SyncContext holds the per object data for SyncChannel, so that SyncChannel
   // can be deleted while it's being used in a different thread.  See
   // ChannelProxy::Context for more information.
-  class SyncContext : public Context,
-                      public base::WaitableEventWatcher::Delegate {
+  class SyncContext : public Context {
    public:
     SyncContext(Listener* listener,
                 base::SingleThreadTaskRunner* ipc_task_runner,
@@ -163,6 +161,8 @@ class IPC_EXPORT SyncChannel : public ChannelProxy,
       return restrict_dispatch_group_;
     }
 
+    base::WaitableEventWatcher::EventCallback MakeWaitableEventCallback();
+
    private:
     virtual ~SyncContext();
     // ChannelProxy methods that we override.
@@ -179,8 +179,7 @@ class IPC_EXPORT SyncChannel : public ChannelProxy,
     // Cancels all pending Send calls.
     void CancelPendingSends();
 
-    // WaitableEventWatcher::Delegate implementation.
-    virtual void OnWaitableEventSignaled(base::WaitableEvent* arg) OVERRIDE;
+    void OnWaitableEventSignaled(base::WaitableEvent* event);
 
     typedef std::deque<PendingSyncMsg> PendingSyncMessageQueue;
     PendingSyncMessageQueue deserializers_;
@@ -190,12 +189,12 @@ class IPC_EXPORT SyncChannel : public ChannelProxy,
 
     base::WaitableEvent* shutdown_event_;
     base::WaitableEventWatcher shutdown_watcher_;
+    base::WaitableEventWatcher::EventCallback shutdown_watcher_callback_;
     int restrict_dispatch_group_;
   };
 
  private:
-  // WaitableEventWatcher::Delegate implementation.
-  virtual void OnWaitableEventSignaled(base::WaitableEvent* arg) OVERRIDE;
+  void OnWaitableEventSignaled(base::WaitableEvent* arg);
 
   SyncContext* sync_context() {
     return reinterpret_cast<SyncContext*>(context());
@@ -217,6 +216,7 @@ class IPC_EXPORT SyncChannel : public ChannelProxy,
 
   // Used to signal events between the IPC and listener threads.
   base::WaitableEventWatcher dispatch_watcher_;
+  base::WaitableEventWatcher::EventCallback dispatch_watcher_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncChannel);
 };