CopyOutputResult must have a working release callback when received over mojo

cc/resources/single_release_callback.cc

 // 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.
 
 #include "cc/resources/single_release_callback.h"
 
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 
 namespace cc {
 
 SingleReleaseCallback::SingleReleaseCallback(const ReleaseCallback& callback)
     : callback_(callback) {
   DCHECK(!callback_.is_null())
       << "Use a NULL SingleReleaseCallback for an empty callback.";
 }
 
+SingleReleaseCallback::SingleReleaseCallback(
+    std::unique_ptr<PtrHolder> ptr_holder)
+    : ptr_holder_(std::move(ptr_holder)) {}
+
 SingleReleaseCallback::~SingleReleaseCallback() {
-  DCHECK(callback_.is_null()) << "SingleReleaseCallback was never run.";
+  DCHECK(callback_.is_null() && !ptr_holder_)

[danakj, 2017/02/08 20:53:31]

split a DCHECK with && into 2 DCHECKs so you can tell which failed

[Saman Sami, 2017/02/08 21:44:21]

Done.

+      << "SingleReleaseCallback was never run.";
 }
 
 void SingleReleaseCallback::Run(const gpu::SyncToken& sync_token,
                                 bool is_lost) {
-  DCHECK(!callback_.is_null())
+  DCHECK(!callback_.is_null() || ptr_holder_)

[danakj, 2017/02/08 20:53:31]

I think this can be written DCHECK(callback_ || ptr_holder_) now which is nicer
without the double negatives

[Saman Sami, 2017/02/08 21:44:21]

Done.

       << "SingleReleaseCallback was run more than once.";
-  base::ResetAndReturn(&callback_).Run(sync_token, is_lost);
+  if (ptr_holder_)
+    ptr_holder_->Release(sync_token, is_lost);
+  else
+    callback_.Run(sync_token, is_lost);
+  ptr_holder_.reset();
+  callback_.Reset();
 }
 
 }  // namespace cc