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/events/Event.h"
+#include "modules/battery/BatteryStatus.h"
+#include <limits>
+
+namespace WebCore {
+
+PassRefPtr<BatteryManager> BatteryManager::create(ExecutionContext* context)
+{
+    return adoptRef(new BatteryManager(context));
+}
+
+BatteryManager::~BatteryManager()
+{
+}
+
+BatteryManager::BatteryManager(ExecutionContext* context)
+    : ContextLifecycleObserver(context)
+    , 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)
+{
+    ASSERT(RuntimeEnabledFeatures::batteryStatusEnabled());
+
+    m_batteryStatus = batteryStatus;
+    dispatchEvent(event);
+}
+
+} // namespace WebCore