Add MJPEG support to FakeVideoCaptureDevice

media/capture/video/fake_video_capture_device.h

Index: media/capture/video/fake_video_capture_device.h
diff --git a/media/capture/video/fake_video_capture_device.h b/media/capture/video/fake_video_capture_device.h
index c853b4dfde712d2cd5752ea597de844305f6695b..1f3147af82bfa7b4c8260bdad9b2eaa063ad3ef4 100644
--- a/media/capture/video/fake_video_capture_device.h
+++ b/media/capture/video/fake_video_capture_device.h
@@ -18,6 +18,7 @@ namespace media {
 // on a given target OutputMode and frame rate.
 class CAPTURE_EXPORT FakeVideoCaptureDeviceMaker {
  public:
+  enum class PixelFormat { I420, Y16, MJPEG };
   enum class DeliveryMode {
     USE_DEVICE_INTERNAL_BUFFERS,
     USE_CLIENT_PROVIDED_BUFFERS
@@ -25,8 +26,11 @@ class CAPTURE_EXPORT FakeVideoCaptureDeviceMaker {
 
   static void GetSupportedSizes(std::vector<gfx::Size>* supported_sizes);
 
+  static media::VideoPixelFormat TranslateToMediaVideoPixelFormat(
+      PixelFormat format);

[mcasas, 2017/02/22 20:26:33]

We already have a |VideoPixelFormat|. I think you want
to limit the ones accepted/supported by this particular
class (and by PacmanFramePainter, where we have 
another redefinition).  Find other way, e.g. DCHECKs,
otherwise the benefits of compile-time checking that
only supported formats are used, are overriden by the
extra code you need to translate back and forth.

[chfremer, 2017/02/23 01:14:28]

You are right. The reason I added these enum classes is as a C++ way to express
that only a certain subset of formats is supported. I feel that doing so is much
better than expressing the same using runtime checks and comments. I don't see
how the need to translate back and forth negates this.

In the new patch set, I am changing one direction of the translation from an
explicit mapping to a static_cast. Please let me know if that eases (or
increases?) the concern about the translation.

When you recommend trying to find a solution using DCHECKs, is there some
alternative you see that does not boil down to runtime checks and comments?

+
   static std::unique_ptr<VideoCaptureDevice> MakeInstance(
-      VideoPixelFormat pixel_format,
+      PixelFormat pixel_format,
       DeliveryMode delivery_mode,
       float frame_rate);
 };