[Blink, RemotePlayback] watchAvailability() implementation.

third_party/WebKit/Source/modules/remoteplayback/RemotePlayback.h

 // Copyright 2016 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.
 
 #ifndef RemotePlayback_h
 #define RemotePlayback_h
 
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 #include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptState.h"
 #include "core/events/EventTarget.h"
 #include "modules/ModulesExport.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/modules/remoteplayback/WebRemotePlaybackClient.h"
 #include "public/platform/modules/remoteplayback/WebRemotePlaybackState.h"
 #include "wtf/Compiler.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class ExecutionContext;
 class HTMLMediaElement;
 class LocalFrame;
-class RemotePlaybackAvailability;
+class RemotePlaybackAvailabilityCallback;
 class ScriptPromiseResolver;
 
 class MODULES_EXPORT RemotePlayback final
     : public EventTargetWithInlineData,
       public ActiveScriptWrappable,
       WTF_NON_EXPORTED_BASE(private WebRemotePlaybackClient) {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(RemotePlayback);
 
  public:
   static RemotePlayback* create(HTMLMediaElement&);
 
   // EventTarget implementation.
   const WTF::AtomicString& interfaceName() const override;
   ExecutionContext* getExecutionContext() const override;
 
-  ScriptPromise getAvailability(ScriptState*);
+  // Starts notifying the page about the changes to the remote playback devices
+  // availability via the provided callback. May start the monitoring of remote
+  // playback devices if it isn't running yet.
+  ScriptPromise watchAvailability(ScriptState*,
+                                  RemotePlaybackAvailabilityCallback*);
+
+  // Cancels updating the page via the callback specified by its id.
+  ScriptPromise cancelWatchAvailability(ScriptState*, int id);
+
+  // Cancels all the callbacks watching remote playback availability changes
+  // registered with this element.
+  ScriptPromise cancelWatchAvailability(ScriptState*);
+
+  // Shows the UI allowing user to change the remote playback state of the media
+  // element (by picking a remote playback device from the list, for example).
   ScriptPromise prompt(ScriptState*);
 
   String state() const;
 
   // ScriptWrappable implementation.
   bool hasPendingActivity() const final;
 
   DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class RemotePlaybackTest;
 
   explicit RemotePlayback(HTMLMediaElement&);
 
+  // Calls the specified availability callback with the current availability.
+  // Need a void() method to post it as a task.

[Zhiqiang Zhang (Slow), 2016/10/13 15:23:11]

s/Need a/Need to be a

+  void notifyInitialAvailability(int callbackId);
+
   // WebRemotePlaybackClient implementation.
   void stateChanged(WebRemotePlaybackState) override;
   void availabilityChanged(bool available) override;
   void promptCancelled() override;
 
+  RefPtr<ScriptState> m_scriptState;
   WebRemotePlaybackState m_state;
   bool m_availability;
-  HeapVector<Member<RemotePlaybackAvailability>> m_availabilityObjects;
+  HeapHashMap<int, Member<RemotePlaybackAvailabilityCallback>>
+      m_availabilityCallbacks;
   Member<HTMLMediaElement> m_mediaElement;
   Member<ScriptPromiseResolver> m_promptPromiseResolver;
 };
 
 }  // namespace blink
 
 #endif  // RemotePlayback_h