arc: Initial implemetation of Chrome sync for Arc packages.

components/arc/instance_holder.h

 // Copyright 2015 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 COMPONENTS_ARC_INSTANCE_HOLDER_H_
 #define COMPONENTS_ARC_INSTANCE_HOLDER_H_
 
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 44 matching lines @@
       observer->OnInstanceReady();
   }
 
   void RemoveObserver(Observer* observer) {
     DCHECK(thread_checker_.CalledOnValidThread());
     observer_list_.RemoveObserver(observer);
   }
 
   // Called when the channel is closed.
   void CloseChannel() {
-    if (!ptr_)
+    if (!ptr_ && !raw_ptr_)

[Luis Héctor Chávez, 2016/07/25 17:31:17]

I prefer if this would only be |!raw_ptr_|, since resetting an already-reset
|ptr_| is a no-op.

[lgcheng, 2016/07/25 20:45:17]

Done.

       return;
 
     ptr_.reset();
     raw_ptr_ = nullptr;
     version_ = 0;
     FOR_EACH_OBSERVER(Observer, observer_list_, OnInstanceClosed());
   }
 
   // Sets the interface pointer to |ptr|, once the version is determined. This
   // will eventually invoke SetInstance(), which will notify the observers.
@@ skipping 42 matching lines @@
   // This needs to be the last member in order to cancel all inflight callbacks
   // before destroying any other members.
   base::WeakPtrFactory<InstanceHolder<T>> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(InstanceHolder<T>);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_INSTANCE_HOLDER_H_