refactor EnumerateDevices to make it a persistent request.

content/renderer/media/media_stream_dispatcher.h

Index: content/renderer/media/media_stream_dispatcher.h
===================================================================
--- content/renderer/media/media_stream_dispatcher.h	(revision 148913)
+++ content/renderer/media/media_stream_dispatcher.h	(working copy)
@@ -52,6 +52,11 @@
       media_stream::MediaStreamType type,
       const GURL& security_origin);
 
+  // Request to stop enumerating devices.
+  void StopEnumerateDevices(
+      int request_id,
+      const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler);
+
   // Request to open a device.
   void OpenDevice(
       int request_id,
@@ -83,6 +88,29 @@
   // opened it.
   struct Stream;
 
+  struct EnumerationRequest {
+    EnumerationRequest(
+        const base::WeakPtr<MediaStreamDispatcherEventHandler>& handler,
+        int request_id);
+
+    base::WeakPtr<MediaStreamDispatcherEventHandler> handler;
+    int request_id;
+  };
+
+  // List of requests made to EnumerateDevices.
+  typedef std::list<EnumerationRequest> EnumerationRequestList;
+
+  struct EnumerationState {
+    EnumerationState();
+
+    bool started;
+    int ipc_id;
+    std::string label;
+    bool cache_valid;
+    media_stream::StreamDeviceInfoArray cached_device;
+    EnumerationRequestList requests;
+  };
+
   // Messages from the browser.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
   void OnStreamGenerated(
@@ -95,6 +123,7 @@
   void OnAudioDeviceFailed(const std::string& label, int index);
   void OnDevicesEnumerated(
       int request_id,
+      const std::string& label,
       const media_stream::StreamDeviceInfoArray& device_array);
   void OnDevicesEnumerationFailed(int request_id);
   void OnDeviceOpened(
@@ -103,10 +132,18 @@
       const media_stream::StreamDeviceInfo& device_info);
   void OnDeviceOpenFailed(int request_id);
 
+  bool RemoveEnumerationRequest(
+      int request_id,
+      const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
+      EnumerationState* state);
+
   int next_ipc_id_;
   typedef std::map<std::string, Stream> LabelStreamMap;
   LabelStreamMap label_stream_map_;
 
+  EnumerationState audio_enumeration_state_;
+  EnumerationState video_enumeration_state_;
+
   // List of calls made to GenerateStream that has not yet completed.
   typedef std::list<Request> RequestList;
   RequestList requests_;