Do not delete blink::WebRTCCertificateCallback on non-main thread

base/sequenced_task_runner.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 BASE_SEQUENCED_TASK_RUNNER_H_
 #define BASE_SEQUENCED_TASK_RUNNER_H_
 
 #include "base/base_export.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/task_runner.h"
@@ skipping 136 matching lines @@
 
   bool DeleteSoonInternal(const tracked_objects::Location& from_here,
                           void(*deleter)(const void*),
                           const void* object);
 
   bool ReleaseSoonInternal(const tracked_objects::Location& from_here,
                            void(*releaser)(const void*),
                            const void* object);
 };
 
+struct BASE_EXPORT OnTaskRunnerDeleter {
+  explicit OnTaskRunnerDeleter(scoped_refptr<SequencedTaskRunner> task_runner);

[hbos_chromium, 2016/07/20 12:42:32]

nit: const scoped_refptr<...>&

[tzik, 2016/07/20 14:37:50]

Newer styleguide prefer the pass-by-value on smart pointers to pass-by-ref.
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

[tzik, 2016/07/20 14:42:26]

Oh... The chromium-style plugin complains we need an explicit out-of-line
copy/move ctor. :-(
Let me readd them.

[hbos_chromium, 2016/07/20 15:15:39]

Acknowledged.

+  ~OnTaskRunnerDeleter();
+
+  OnTaskRunnerDeleter(OnTaskRunnerDeleter&&);
+  OnTaskRunnerDeleter& operator=(OnTaskRunnerDeleter&&);
+
+  template <typename T>
+  void operator()(const T* ptr) {
+    if (task_runner_->RunsTasksOnCurrentThread())
+      delete ptr;
+    else if (ptr)
+      task_runner_->DeleteSoon(FROM_HERE, ptr);
+  }
+
+  scoped_refptr<SequencedTaskRunner> task_runner_;
+};
+
 }  // namespace base
 
 #endif  // BASE_SEQUENCED_TASK_RUNNER_H_