RequestIdleCallback: Avoid retaining ScriptedIdleTaskController while a cancelled timeout is pending

third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.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 "core/dom/ScriptedIdleTaskController.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/IdleRequestCallback.h"
 #include "core/dom/IdleRequestOptions.h"
 #include "core/inspector/InspectorTraceEvents.h"
@@ skipping 16 matching lines @@
     {
         return adoptRef(new IdleRequestCallbackWrapper(id, controller));
     }
     virtual ~IdleRequestCallbackWrapper()
     {
     }
 
     static void idleTaskFired(PassRefPtr<IdleRequestCallbackWrapper> callbackWrapper, double deadlineSeconds)
     {
         // TODO(rmcilroy): Implement clamping of deadline in some form.
-        callbackWrapper->controller()->callbackFired(callbackWrapper->id(), deadlineSeconds, IdleDeadline::CallbackType::CalledWhenIdle);
+        if (callbackWrapper->controller())

[esprehn, 2016/03/16 16:32:18]

We normally assign to a local in the if to avoid the verbosity and  make the
scope clear.

if (Foo* foo = thing->foo())
    foo->...

[rmcilroy, 2016/03/16 16:40:15]

Done.

+            callbackWrapper->controller()->callbackFired(callbackWrapper->id(), deadlineSeconds, IdleDeadline::CallbackType::CalledWhenIdle);
+        callbackWrapper->cancel();
     }
 
     static void timeoutFired(PassRefPtr<IdleRequestCallbackWrapper> callbackWrapper)
     {
-        callbackWrapper->controller()->callbackFired(callbackWrapper->id(), monotonicallyIncreasingTime(), IdleDeadline::CallbackType::CalledByTimeout);
+        if (callbackWrapper->controller())
+            callbackWrapper->controller()->callbackFired(callbackWrapper->id(), monotonicallyIncreasingTime(), IdleDeadline::CallbackType::CalledByTimeout);
+        callbackWrapper->cancel();
+    }
+
+    void cancel()
+    {
+        m_controller = nullptr;
     }
 
     ScriptedIdleTaskController::CallbackId id() const { return m_id; }
     PassRefPtrWillBeRawPtr<ScriptedIdleTaskController> controller() const { return m_controller; }
 
 private:
     IdleRequestCallbackWrapper(ScriptedIdleTaskController::CallbackId id, PassRefPtrWillBeRawPtr<ScriptedIdleTaskController> controller)
         : m_id(id)
         , m_controller(controller)
     {
@@ skipping 105 matching lines @@
         runCallback(id, monotonicallyIncreasingTime(), IdleDeadline::CallbackType::CalledByTimeout);
 
     // Repost idle tasks for any remaining callbacks.
     for (auto& callback : m_callbacks) {
         RefPtr<internal::IdleRequestCallbackWrapper> callbackWrapper = internal::IdleRequestCallbackWrapper::create(callback.key, this);
         m_scheduler->postIdleTask(BLINK_FROM_HERE, WTF::bind<double>(&internal::IdleRequestCallbackWrapper::idleTaskFired, callbackWrapper));
     }
 }
 
 } // namespace blink