Make sure MediaStreamManager handles requests in order.

content/browser/renderer_host/media/media_stream_manager.h

 // Copyright (c) 2012 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.
 
 // MediaStreamManager is used to open/enumerate media capture devices (video
 // supported now). Call flow:
 // 1. GenerateStream is called when a render process wants to use a capture
 //    device.
 // 2. MediaStreamManager will ask MediaStreamUIController for permission to
 //    use devices and for which device to use.
 // 3. MediaStreamManager will request the corresponding media device manager(s)
 //    to enumerate available devices. The result will be given to
 //    MediaStreamUIController.
 // 4. MediaStreamUIController will, by posting the request to UI, let the
 //    users to select which devices to use and send callback to
 //    MediaStreamManager with the result.
 // 5. MediaStreamManager will call the proper media device manager to open the
 //    device and let the MediaStreamRequester know it has been done.
 
 // If either user or test harness selects --use-fake-device-for-media-stream,
 // a fake video device or devices are used instead of real ones.
 
 // When enumeration and open are done in separate operations,
 // MediaStreamUIController is not involved as in steps.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_MANAGER_H_
 
-#include <map>
+#include <list>
 #include <set>
 #include <string>
+#include <utility>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/power_monitor/power_observer.h"
 #include "base/system_monitor/system_monitor.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
@@ skipping 179 matching lines @@
 
   // Cache enumerated device list.
   struct EnumerationCache {
     EnumerationCache();
     ~EnumerationCache();
 
     bool valid;
     StreamDeviceInfoArray devices;
   };
 
-  typedef std::map<std::string, DeviceRequest*> DeviceRequests;
+  // |DeviceRequests| is a list to ensure requests are processed in the order
+  // they arrive. The first member of the pair is the label of the
+  // |DeviceRequest|.
+  typedef std::list<std::pair<std::string, DeviceRequest*> > DeviceRequests;
 
   // Initializes the device managers on IO thread.  Auto-starts the device
   // thread and registers this as a listener with the device managers.
   void InitializeDeviceManagersOnIOThread();
 
   // Helper for sending up-to-date device lists to media observer when a
   // capture device is plugged in or unplugged.
   void NotifyDevicesChanged(MediaStreamType stream_type,
                             const StreamDeviceInfoArray& devices);
 
@@ skipping 147 matching lines @@
 
   bool use_fake_ui_;
   scoped_ptr<FakeMediaStreamUIProxy> fake_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_MANAGER_H_