Add still image capture interface for VideoCaptureDevice.

media/video/capture/video_capture_device.h

Index: media/video/capture/video_capture_device.h
diff --git a/media/video/capture/video_capture_device.h b/media/video/capture/video_capture_device.h
index 382dad6cdc461d7d6d20bf04ab8e7e91693ae503..fff3243fdfc210775f41ee6ffb363a55f5c69121 100644
--- a/media/video/capture/video_capture_device.h
+++ b/media/video/capture/video_capture_device.h
@@ -216,6 +216,30 @@ class MEDIA_EXPORT VideoCaptureDevice {
 
     // VideoCaptureDevice requests the |message| to be logged.
     virtual void OnLog(const std::string& message) {}
+
+    // The video stream is being muted. After this callback, no more

[wuchengli, 2014/09/09 05:53:22]

s/is being/has/

[Owen Lin, 2014/09/11 06:17:59]

Done.

+    // OnIncomingCapturedData() will be called.

[wuchengli, 2014/09/09 05:53:21]

Explain OnMute and OnUnmute are called when image capture is started and ended
is called.

[Owen Lin, 2014/09/11 06:17:59]

Done.

+    virtual void OnMute() {}
+
+    // The video stream is being resumed.

[wuchengli, 2014/09/09 05:53:22]

s/is being/has/

[Owen Lin, 2014/09/11 06:18:00]

Done.

+    virtual void OnUnmute() {}
+  };
+
+  class MEDIA_EXPORT ImageClient {
+   public:
+    virtual ~ImageClient() {}
+
+    // Callback function to notify the client the caputred image is available.
+    virtual void OnIncomingCapturedData(const uint8* data,
+                                        int length,
+                                        const ImageCaptureFormat& format,
+                                        int rotation,
+                                        base::TimeTicks timestamp) = 0;
+
+    // Callback function to notify client the failure of the image capturing.
+    // The VideoCaptureDevice must be StopAndDeAllocate()-ed. |reason| is a

[wuchengli, 2014/09/09 05:53:22]

s/StopAndDeAllocate/CloseImageCapture/

[Owen Lin, 2014/09/11 06:17:59]

I do mean StopAndDeallocate. In the current implementation, the device would go
to an error state and has to be restart again. No error is expected so I don't
think we need to spend too much effort in resuming from the error state for
still image capture.

+    // text description of the error.
+    virtual void OnError(const std::string& reason) = 0;
   };
 
   // Creates a VideoCaptureDevice object.
@@ -235,6 +259,12 @@ class MEDIA_EXPORT VideoCaptureDevice {
   static void GetDeviceSupportedFormats(const Name& device,
                                         VideoCaptureFormats* supported_formats);
 
+  // Gets the supported formats for still image of a particular device attached
+  // to the system.
+  static void GetDeviceSupportedImageFormats(
+      const Name& device,
+      ImageCaptureFormats* supported_formats);
+
   // Prepares the camera for use. After this function has been called no other
   // applications can use the camera. StopAndDeAllocate() must be called before
   // the object is deleted.
@@ -258,6 +288,21 @@ class MEDIA_EXPORT VideoCaptureDevice {
   // defined, otherwise returns 0.
   int GetPowerLineFrequencyForLocation() const;
 
+  // Initializes the device for still image capture for the given image format.
+  // This function is used to allocate resources.

[wuchengli, 2014/09/09 05:53:22]

Does the caller require to start the video stream first to use image capture?

[Owen Lin, 2014/09/11 06:17:59]

Yes. Comment added.

+  virtual void InitializeImageCapture(const ImageCaptureFormat& image_format,

[wuchengli, 2014/09/09 05:53:22]

Using AllocateImageCapture and DeAllocateImageCapture is more consistent?

[Owen Lin, 2014/09/11 06:17:59]

The problem is we may not really allocate resources here (like the current
implementation).

+                                      scoped_ptr<ImageClient> client);
+
+  // Releases used resources for image capture.

[wuchengli, 2014/09/09 05:53:22]

s/used//

Does CloseImageCapture have to be called before the object is deleted like
StopAndDeAllocate? Or the destructor handles it?

[Owen Lin, 2014/09/11 06:18:00]

Command added. It has to be called before StopAndDeAllocate().

+  virtual void CloseImageCapture() {}
+
+  // Gets one image from the device. It will returne the picture by the

[wuchengli, 2014/09/09 05:53:21]

s/returne/return/. s/picture/image/.

[Owen Lin, 2014/09/11 06:18:00]

Done.

+  // ImageClient's OnIncomingCapturedData() callback.

[wuchengli, 2014/09/09 05:53:21]

ImageClient::OnIncomingCapturedData(). Also mention OnMute and OnUnmute will be
called.

[Owen Lin, 2014/09/11 06:17:59]

Done.

+  //
+  // This function must be called between InitializeImageCapture() and
+  // CloseImageCapture().
+  virtual void CaptureImage() {}
+
  protected:
   static const int kPowerLine50Hz = 50;
   static const int kPowerLine60Hz = 60;