Add Dispatcher class to the Battery Status API module.

Source/modules/battery/BatteryManager.cpp

Index: Source/modules/battery/BatteryManager.cpp
diff --git a/Source/modules/battery/BatteryManager.cpp b/Source/modules/battery/BatteryManager.cpp
index aa473753d2be64beff8fe1e66d389d25c920a1fe..552fc8b9baea36f6d84c8826aa0176685e37e8d4 100644
--- a/Source/modules/battery/BatteryManager.cpp
+++ b/Source/modules/battery/BatteryManager.cpp
@@ -7,6 +7,7 @@
 
 #include "RuntimeEnabledFeatures.h"
 #include "core/events/Event.h"
+#include "modules/battery/BatteryDispatcher.h"
 #include "modules/battery/BatteryStatus.h"
 #include <limits>
 
@@ -14,58 +15,108 @@ namespace WebCore {
 
 PassRefPtrWillBeRawPtr<BatteryManager> BatteryManager::create(ExecutionContext* context)
 {
-    return adoptRefWillBeRefCountedGarbageCollected(new BatteryManager(context));
+    RefPtrWillBeRawPtr<BatteryManager> batteryManager(adoptRefWillBeRefCountedGarbageCollected(new BatteryManager(context)));
+    batteryManager->suspendIfNeeded();
+    return batteryManager.release();
 }
 
 BatteryManager::~BatteryManager()
 {
+    stopUpdating();
 }
 
 BatteryManager::BatteryManager(ExecutionContext* context)
-    : ContextLifecycleObserver(context)
-    , m_batteryStatus(nullptr)
+    : ActiveDOMObject(context)
+    , DeviceSensorEventController(*toDocument(context))
 {
+    // Need to figure out a way to startUpdating only afters EventListeners are added: didAddEventListener?

[timvolodine, 2014/04/09 18:59:02]

also, we need to think about this as it might be a problem. events could get
lost if no listener is registered at the time of callback..

+    m_hasEventListener = true;
+    startUpdating();
 }
 
 bool BatteryManager::charging()
 {
-    return m_batteryStatus ? m_batteryStatus->charging() : true;
+    if (const BatteryStatus* lastData = BatteryDispatcher::instance().getLatestData())
+        return lastData->charging();
+
+    return true;
 }
 
 double BatteryManager::chargingTime()
 {
-    if (!m_batteryStatus)
-        return 0;
-
-    if (!m_batteryStatus->charging())
-        return std::numeric_limits<double>::infinity();
+    if (const BatteryStatus* lastData = BatteryDispatcher::instance().getLatestData()) {
+        // 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(lastData->level() != 1.0 && lastData->chargingTime() == 0.0);

[timvolodine, 2014/04/09 15:19:18]

please remove this assert, as you mention in the comment it is the task of the
'backend' to provide proper data, the task here is just to propagate.

[Srini, 2014/04/09 16:09:57]

Ok.

 
-    // 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 lastData->chargingTime();
+    }
 
-    return m_batteryStatus->chargingTime();
+    return 0;

[timvolodine, 2014/04/09 15:19:18]

should this be infinity as below?

[Srini, 2014/04/09 16:09:57]

I think that default is 0 when the charging default is true. I filled in the
default values from the spec. This is what the assert checks above.

[timvolodine, 2014/04/09 18:59:02]

I thought the default was +inf, but looking at the spec now you are probably
right.

 }
 
 double BatteryManager::dischargingTime()
 {
-    if (!m_batteryStatus || m_batteryStatus->charging())
-        return std::numeric_limits<double>::infinity();
+    if (const BatteryStatus* lastData = BatteryDispatcher::instance().getLatestData())
+        return lastData->dischargingTime();
 
-    return m_batteryStatus->dischargingTime();
+    return std::numeric_limits<double>::infinity();
 }
 
 double BatteryManager::level()
 {
-    return m_batteryStatus ? m_batteryStatus->level() : 1;
+    if (const BatteryStatus* lastData = BatteryDispatcher::instance().getLatestData())
+        return lastData->level();
+
+    return 1;
 }
 
-void BatteryManager::didChangeBatteryStatus(PassRefPtrWillBeRawPtr<Event> event, PassOwnPtr<BatteryStatus> batteryStatus)
+void BatteryManager::didChangeBatteryStatus(PassRefPtrWillBeRawPtr<Event> event)
 {
     ASSERT(RuntimeEnabledFeatures::batteryStatusEnabled());
 
-    m_batteryStatus = batteryStatus;
     dispatchEvent(event);
 }
 
+void BatteryManager::registerWithDispatcher()
+{
+    BatteryDispatcher::instance().addClient(this);
+}
+
+void BatteryManager::unregisterWithDispatcher()
+{
+    BatteryDispatcher::instance().removeClient(this);
+}
+
+bool BatteryManager::hasLastData()
+{
+    return false;

[timvolodine, 2014/04/09 15:19:18]

call to dispatcher.
I've uploaded https://codereview.chromium.org/231003002/ to allow overrides of
dispatchDeviceEvent(), please override it in this class to call dispatchEvent
(instead of the DOMWindow as by default).

[Srini, 2014/04/09 16:09:57]

Ill add this once your patch lands. Thanks for this.

+}
+
+PassRefPtrWillBeRawPtr<Event> BatteryManager::getLastEvent()
+{
+    // We would fire events directly.
+    return nullptr;

[timvolodine, 2014/04/09 15:19:18]

call to dispatcher + return create event

[Srini, 2014/04/09 16:09:57]

I think I need some help here. Now that I was trying to incorporate this, this
will be called startUpdating runs. But this will send only one event. I may be
required to send more than one. I was thinking that I should return null here,
and  I will send 4 events for all the 4 properties in the overridden function
(there is no way to figure out what changed since we last stopped updating). Or
should I store something (which I removed). Or am I confusing it? What do you
think?

[timvolodine, 2014/04/09 18:59:02]

yeah, I see the problem. The DeviceSensorEventController was designed to fire
only one event. I guess you could circumvent this by having nullptr here and
making sure the overriden dispatchDeviceEvent() method dispatches all events
when called with null. Alternatively we could consider extending getLastEvent to
getLastEvents and return multiple events there, but that would require some
refactoring.

+}
+
+bool BatteryManager::isNullEvent(Event*)
+{
+    return true;

[timvolodine, 2014/04/09 15:19:18]

return false;
I don't think we have the concept of null events for battery.

[Srini, 2014/04/09 16:09:57]

Ok.

+}
+
+void BatteryManager::suspend()
+{
+    stopUpdating();
+}
+
+void BatteryManager::resume()
+{
+    startUpdating();
+}
+
+void BatteryManager::stop()
+{
+    stopUpdating();
+}
+
 } // namespace WebCore