Implement requestIdleCallback API

Source/core/dom/IdleCallbackDeadline.cpp

Index: Source/core/dom/IdleCallbackDeadline.cpp
diff --git a/Source/core/dom/IdleCallbackDeadline.cpp b/Source/core/dom/IdleCallbackDeadline.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..73ab4d1c3c157297fc238a9d57c0b8cb86b7aad9
--- /dev/null
+++ b/Source/core/dom/IdleCallbackDeadline.cpp
@@ -0,0 +1,26 @@
+// 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 now = 1000 * m_timing.monotonicTimeToZeroBasedDocumentTime(monotonicallyIncreasingTime());
+    return m_deadlineMillis - now;
+}
+
+} // namespace blink