BatteryStatus: fix chargingTime() to follow the specification.

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"
@@ skipping 16 matching lines @@
 {
 }
 
 bool BatteryManager::charging()
 {
     return m_batteryStatus ? m_batteryStatus->charging() : true;
 }
 
 double BatteryManager::chargingTime()
 {
-    if (!m_batteryStatus || !m_batteryStatus->charging())
+    if (!m_batteryStatus)
+        return 0;
+
+    if (!m_batteryStatus->charging())
         return std::numeric_limits<double>::infinity();
 
+    // The spec requires that if level == 1.0, chargingTime == 0 but this has to
+    // be implement by the backend. Adding this assert will help enforcing it.
+    ASSERT(level() != 1.0 && m_batteryStatus->chargingTime() == 0.0);
+
     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