Cancel a task associated to TaskHandle when the TaskHandle is overridden

third_party/WebKit/Source/platform/WebTaskRunner.cpp

 // 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.
 
 #include "platform/WebTaskRunner.h"
 
 #include "base/single_thread_task_runner.h"
 
 namespace blink {
 
@@ skipping 53 matching lines @@
   }
 }
 
 TaskHandle::TaskHandle() = default;
 
 TaskHandle::~TaskHandle() {
   cancel();
 }
 
 TaskHandle::TaskHandle(TaskHandle&&) = default;
-TaskHandle& TaskHandle::operator=(TaskHandle&&) = default;
+
+TaskHandle& TaskHandle::operator=(TaskHandle&& other) {
+  TaskHandle tmp(std::move(other));
+  m_runner.swap(tmp.m_runner);
+  return *this;
+}
 
 TaskHandle::TaskHandle(RefPtr<Runner> runner) : m_runner(std::move(runner)) {
   DCHECK(m_runner);
 }
 
 void WebTaskRunner::postTask(const WebTraceLocation& location,
                              std::unique_ptr<CrossThreadClosure> task) {
   toSingleThreadTaskRunner()->PostTask(location,
                                        convertToBaseCallback(std::move(task)));
 }
@@ skipping 38 matching lines @@
   DCHECK(runsTasksOnCurrentThread());
   RefPtr<TaskHandle::Runner> runner =
       adoptRef(new TaskHandle::Runner(std::move(task)));
   postDelayedTask(location, WTF::bind(&TaskHandle::Runner::run,
                                       runner->asWeakPtr(), TaskHandle(runner)),
                   delayMs);
   return TaskHandle(runner);
 }
 
 }  // namespace blink