ImageCapture: Implement takePhoto() for Mac AVFoundation

media/capture/video/mac/video_capture_device_mac.h

Index: media/capture/video/mac/video_capture_device_mac.h
diff --git a/media/capture/video/mac/video_capture_device_mac.h b/media/capture/video/mac/video_capture_device_mac.h
index 88b986b6fa0a5dcc66e848a8d0c97101d8a358d6..0af8929c00ad3455d97911715ea16c1c21f4dab8 100644
--- a/media/capture/video/mac/video_capture_device_mac.h
+++ b/media/capture/video/mac/video_capture_device_mac.h
@@ -62,10 +62,12 @@ class VideoCaptureDeviceMac : public VideoCaptureDevice {
       const VideoCaptureParams& params,
       std::unique_ptr<VideoCaptureDevice::Client> client) override;
   void StopAndDeAllocate() override;
+  void TakePhoto(TakePhotoCallback callback) override;
 
   bool Init(VideoCaptureDevice::Name::CaptureApiType capture_api_type);
 
-  // Called to deliver captured video frames.
+  // Called to deliver captured video frames.  It's safe to call this method
+  // from any thread, including those controlled by AVFoundation.
   void ReceiveFrame(const uint8_t* video_frame,
                     int video_frame_length,
                     const VideoCaptureFormat& frame_format,
@@ -73,6 +75,13 @@ class VideoCaptureDeviceMac : public VideoCaptureDevice {
                     int aspect_denominator,
                     base::TimeDelta timestamp);
 
+  // Callbacks with the result of a still image capture, or in case of error,
+  // respectively. It's safe to call these methods from any thread.
+  void OnPhotoTaken(const uint8_t* image_data,
+                    int image_length,

[Robert Sesek, 2016/07/08 19:31:04]

Lengths should generally be size_t.

[mcasas, 2016/07/08 21:39:28]

Done.

+                    const std::string& mime_type);
+  void OnPhotoError();
+
   // Forwarder to VideoCaptureDevice::Client::OnError().
   void ReceiveError(const tracked_objects::Location& from_here,
                     const std::string& reason);
@@ -99,6 +108,9 @@ class VideoCaptureDeviceMac : public VideoCaptureDevice {
 
   base::scoped_nsobject<VideoCaptureDeviceAVFoundation> capture_device_;
 
+  // To hold on to the TakePhotoCallback while the picture is being taken.
+  std::unique_ptr<TakePhotoCallback> photo_callback_;
+
   // Used with Bind and PostTask to ensure that methods aren't called after the
   // VideoCaptureDeviceMac is destroyed.
   // NOTE: Weak pointers must be invalidated before all other member variables.