Rename IdleCallbackDeadline to IdleDeadline to be in sync with spec.

Source/core/dom/IdleDeadline.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 "config.h"
-#include "core/dom/IdleCallbackDeadline.h"
+#include "core/dom/IdleDeadline.h"
 
 #include "wtf/CurrentTime.h"
 
 namespace blink {
 
-IdleCallbackDeadline::IdleCallbackDeadline(double deadlineSeconds, CallbackType callbackType)
+IdleDeadline::IdleDeadline(double deadlineSeconds, CallbackType callbackType)
     : m_deadlineSeconds(deadlineSeconds)
     , m_callbackType(callbackType)
 {
 }
 
-double IdleCallbackDeadline::timeRemaining() const
+double IdleDeadline::timeRemaining() const
 {
     double timeRemaining = m_deadlineSeconds - monotonicallyIncreasingTime();
     if (timeRemaining < 0)
         timeRemaining = 0;
 
     return timeRemaining * 1000;
 }
 
 } // namespace blink