Battery Status API: blink promise implementation and layout tests.

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 4e6d5a94fa6e329c96e74f6ed5f775a3f46a775a..577ddc0e713f4ffc3956e9e936b124443c5b5001 100644
--- a/Source/modules/battery/BatteryManager.cpp
+++ b/Source/modules/battery/BatteryManager.cpp
@@ -18,6 +18,29 @@ PassRefPtrWillBeRawPtr<BatteryManager> BatteryManager::create(ExecutionContext*
     return batteryManager.release();
 }
 
+class BatteryManager::ThenFunction FINAL : public ScriptFunction {
+public:
+    static PassOwnPtr<ScriptFunction> create(PassRefPtr<BatteryManager> observer)
+    {
+        ExecutionContext* executionContext = observer->executionContext();
+        return adoptPtr(new ThenFunction(toIsolate(executionContext), observer));
+    }
+private:
+    ThenFunction(v8::Isolate* isolate, PassRefPtr<BatteryManager> observer)
+        : ScriptFunction(isolate)
+        , m_observer(observer)
+    {
+    }
+
+    virtual ScriptValue call(ScriptValue value) OVERRIDE
+    {
+        m_observer->onPromiseResolved();
+        return value;
+    }
+
+    RefPtr<BatteryManager> m_observer;
+};
+
 BatteryManager::~BatteryManager()
 {
     stopUpdating();
@@ -27,9 +50,34 @@ BatteryManager::BatteryManager(ExecutionContext* context)
     : ActiveDOMObject(context)
     , DeviceEventControllerBase(toDocument(context)->page())
     , m_batteryStatus(BatteryStatus::create())
+    , m_state(NotStarted)
+{
+}
+
+ScriptPromise BatteryManager::startRequest(ScriptState* scriptState)
 {
+    if (m_state == Pending)
+        return m_resolver->promise();
+
+    m_resolver = ScriptPromiseResolverWithContext::create(scriptState);
+    ScriptPromise promise = m_resolver->promise();
+
+    if (m_state == Resolved) {
+        m_resolver->resolve(this);
+        return promise;
+    }

[abarth-chromium, 2014/06/11 19:44:34]

Why not just return m_resolver->promise(); at this point?

[timvolodine, 2014/06/12 16:38:45]

slightly refactored this code. Done.

+
+    m_state = Pending;
     m_hasEventListener = true;
+    promise.then(ThenFunction::create(this));

[abarth-chromium, 2014/06/11 19:44:34]

Why do we need to create a ThenFunction instead of just setting m_state =
Resolved near line 116?

[timvolodine, 2014/06/12 16:38:45]

yeah on second thought the "ThenFunction" seems like overkill. Done.

     startUpdating();
+    return promise;
+}
+
+void BatteryManager::onPromiseResolved()
+{
+    ASSERT(m_state == Pending);
+    m_state = Resolved;
 }
 
 bool BatteryManager::charging()
@@ -55,6 +103,7 @@ double BatteryManager::level()
 void BatteryManager::didUpdateData()
 {
     ASSERT(RuntimeEnabledFeatures::batteryStatusEnabled());
+    ASSERT(m_state != NotStarted);
 
     RefPtr<BatteryStatus> oldStatus = m_batteryStatus;
     m_batteryStatus = BatteryDispatcher::instance().latestData();
@@ -62,6 +111,12 @@ void BatteryManager::didUpdateData()
     // BatteryDispatcher also holds a reference to m_batteryStatus.
     ASSERT(m_batteryStatus->refCount() > 1);
 
+    if (m_state == Pending && m_resolver) {
+        ASSERT(m_resolver);
+        m_resolver->resolve(this);
+        return;
+    }
+
     Document* document = toDocument(executionContext());
     if (document->activeDOMObjectsAreSuspended() || document->activeDOMObjectsAreStopped())
         return;