RequestIdleCallback: Avoid retaining ScriptedIdleTaskController while a cancelled timeout is pending

third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp

Index: third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp
diff --git a/third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp b/third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp
index b0bdb09aeb8c4f3fada72a03476c28700fc39e66..4c8427651bbf1e3c2a1a1c1cf08428663b437168 100644
--- a/third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp
+++ b/third_party/WebKit/Source/core/dom/ScriptedIdleTaskController.cpp
@@ -34,12 +34,21 @@ public:
     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; }