Implement requestIdleCallback API

Source/core/dom/IdleCallbackDeadline.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/loader/DocumentLoadTiming.h"
+#include "wtf/CurrentTime.h"
+
+namespace blink {
+
+IdleCallbackDeadline::IdleCallbackDeadline(double deadlineMillis, CallbackType callbackType, const DocumentLoadTiming& timing)
+    : m_deadlineMillis(deadlineMillis)
+    , m_callbackType(callbackType)
+    , m_timing(timing)
+{
+}
+
+double IdleCallbackDeadline::timeRemaining() const
+{
+    double timeRemaining = m_deadlineMillis - (1000 * m_timing.monotonicTimeToZeroBasedDocumentTime(monotonicallyIncreasingTime()));
+    if (timeRemaining < 0)
+        timeRemaining = 0;
+    return timeRemaining;
+}
+
+} // namespace blink