Allow client to request NV12 for video capture

The client is using the supported pixel format reported
by the capture device to start capturing, NV12 is
supported by some capture devices on Chrome OS and virtual
capture devices. So we should allow the client to request
NV12 as the capture pixel format.

      device

Bug: b/166284508
Test: Manually on Cast device that use NV12 virtual capture
Change-Id: I8fd713ec46c52f49928bed5fedc51bdcc342c855
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416757Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809424}

content/browser/renderer_host/media/video_capture_controller.cc

@@ -294,7 +294,8 @@ void VideoCaptureController::AddClient(
   if (!params.IsValid() ||
       !(params.requested_format.pixel_format == media::PIXEL_FORMAT_I420 ||
         params.requested_format.pixel_format == media::PIXEL_FORMAT_Y16 ||
-        params.requested_format.pixel_format == media::PIXEL_FORMAT_ARGB)) {
+        params.requested_format.pixel_format == media::PIXEL_FORMAT_ARGB ||
+        params.requested_format.pixel_format == media::PIXEL_FORMAT_NV12)) {
     // Crash in debug builds since the renderer should not have asked for
     // invalid or unsupported parameters.
     LOG(DFATAL) << "Invalid or unsupported video capture parameters requested: "