Add support to Battery Status API in blink.

Source/modules/battery/BatteryManager.cpp

+// Copyright 2014 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 "modules/battery/BatteryManager.h"
+
+#include "RuntimeEnabledFeatures.h"
+#include "core/dom/Document.h"
+#include "core/events/Event.h"
+#include "core/frame/Frame.h"
+#include "core/frame/Navigator.h"
+#include "modules/battery/BatteryStatus.h"
+#include <limits>
+
+namespace WebCore {
+
+PassRefPtr<BatteryManager> BatteryManager::create(Frame* frame)
+{
+    RefPtr<BatteryManager> batteryManager(adoptRef(new BatteryManager(frame)));
+    batteryManager->suspendIfNeeded();
+    return batteryManager.release();
+}
+
+BatteryManager::~BatteryManager()
+{
+}
+
+BatteryManager::BatteryManager(Navigator* navigator)
+    : ActiveDOMObject(navigator->frame()->document())
+    , m_batteryStatus(nullptr)
+{
+}
+
+BatteryManager::BatteryManager(Frame* frame)
+    : ActiveDOMObject(frame->document())

[abarth-chromium, 2014/02/28 06:45:14]

Notice that this base class (and ContextDestructionObserver) want a Document as
the context object.  Rather than fighting with them, you should take a Document
as an argument.

+    , m_batteryStatus(nullptr)
+{
+}
+
+bool BatteryManager::charging()
+{
+    return m_batteryStatus ? m_batteryStatus->charging() : true;
+}
+
+double BatteryManager::chargingTime()
+{
+    if (!m_batteryStatus || !m_batteryStatus->charging())
+        return std::numeric_limits<double>::infinity();
+
+    return m_batteryStatus->chargingTime();
+}
+
+double BatteryManager::dischargingTime()
+{
+    if (!m_batteryStatus || m_batteryStatus->charging())
+        return std::numeric_limits<double>::infinity();
+
+    return m_batteryStatus->dischargingTime();
+}
+
+double BatteryManager::level()
+{
+    return m_batteryStatus ? m_batteryStatus->level() : 1;
+}
+
+void BatteryManager::didChangeBatteryStatus(PassRefPtr<Event> event, PassOwnPtr<BatteryStatus> batteryStatus)
+{
+    if (RuntimeEnabledFeatures::batteryStatusEnabled()) {

[abarth-chromium, 2014/02/28 06:45:14]

This check isn't correct.  Instead, you should just

ASSERT(RuntimeEnabledFeatures::batteryStatusEnabled());

It ought to be an error to call this function if this feature isn't enabled.

+        m_batteryStatus = batteryStatus;
+        dispatchEvent(event);
+    }
+}
+
+void BatteryManager::suspend()
+{
+    /* Stop listening from the Controller */
+}
+
+void BatteryManager::resume()
+{
+    /* Start listening to the Controller */
+}
+
+void BatteryManager::stop()
+{
+    /* Stop listening from the Controller */
+}

[abarth-chromium, 2014/02/28 06:45:14]

Please remove these functions.  We can add them in a future CL when they do
something.

+
+} // namespace WebCore
+