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 now = 1000 * m_timing.monotonicTimeToZeroBasedDocumentTime(monotonicallyIncreasingTime());
+    return m_deadlineMillis - now;

[esprehn, 2015/08/21 08:22:20]

Won't this go negative after the deadline is hit? That'll make loops like:

while (thing.timeRemaining) { }

into infinite loops if you miss the 0 mark. I guess you're trying to show how
much over the deadline you went? Hmm, like it hitting 0 better.

[rmcilroy, 2015/08/21 11:21:52]

Yeah, makes sense. Done (I'll update the spec to specify this too).

+}
+
+} // namespace blink