Queue commands to the Os to start a video device.

content/browser/renderer_host/media/video_capture_manager.h

Index: content/browser/renderer_host/media/video_capture_manager.h
diff --git a/content/browser/renderer_host/media/video_capture_manager.h b/content/browser/renderer_host/media/video_capture_manager.h
index 58ed04b6be5e8040f65fca8f6a3ca006a32ff19a..7ada66b27dc63218132ffe9019ec3a4d03db906a 100644
--- a/content/browser/renderer_host/media/video_capture_manager.h
+++ b/content/browser/renderer_host/media/video_capture_manager.h
@@ -12,6 +12,7 @@
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 
+#include <list>
 #include <map>
 #include <set>
 #include <string>
@@ -182,6 +183,19 @@ class CONTENT_EXPORT VideoCaptureManager : public MediaStreamProvider {
       const media::VideoCaptureDeviceInfos& old_device_info_cache,
       scoped_ptr<media::VideoCaptureDevice::Names> names_snapshot);
 
+  // On the OS level, starting a capture device can take 1-2 seconds.
+  // To avoid multiple unnecessary start/stop commands to the OS, each start
+  // request is queued in |device_start_queue_|.
+  // QueueStartDevice creates a new entry in |device_start_queue_| and posts a
+  // request to start |entry| on the device thread unless there is another
+  // request pending start.
+  void QueueStartDevice(media::VideoCaptureSessionId session_id,
+                        DeviceEntry* entry,

[tommi (sloooow) - chröme, 2014/12/15 16:25:05]

can you document the ownership/lifetime of |entry|?

+                        const media::VideoCaptureParams& params);
+  void OnDeviceStarted();
+  void DoStopDevice(DeviceEntry* entry, bool delete_entry);
+  void HandleQueuedStartRequest();
+
   // Creates and Starts a new VideoCaptureDevice, storing the result in
   // |entry->video_capture_device|. Ownership of |client| passes to
   // the device.
@@ -245,8 +259,24 @@ class CONTENT_EXPORT VideoCaptureManager : public MediaStreamProvider {
     scoped_ptr<media::VideoCaptureDevice> video_capture_device;
   };
   typedef std::set<DeviceEntry*> DeviceEntries;
+  // Currently opened devices. The device may or may not be started.
   DeviceEntries devices_;
 
+  // On the OS level, starting a capture device can take 1-2 seconds.
+  // To avoid multiple unnecessary start/stop commands to the OS, each start
+  // request is queued in a CaptureDeviceStartRequest.
+  struct CaptureDeviceStartRequest {
+    CaptureDeviceStartRequest(DeviceEntry* device_entry,
+                              media::VideoCaptureSessionId session_id,
+                              const media::VideoCaptureParams& params);
+
+    DeviceEntry* device_entry;

[tommi (sloooow) - chröme, 2014/12/15 16:25:05]

ownership/scope?

+    media::VideoCaptureSessionId session_id;
+    media::VideoCaptureParams params;
+  };
+  typedef std::list<CaptureDeviceStartRequest> DeviceStartQueue;
+  DeviceStartQueue device_start_queue_;
+
   // Device creation factory injected on construction from MediaStreamManager or
   // from the test harness.
   scoped_ptr<media::VideoCaptureDeviceFactory> video_capture_device_factory_;