Do not rotate frames from external cameras

media/capture/video/linux/video_capture_device_chromeos.cc

Index: media/capture/video/linux/video_capture_device_chromeos.cc
diff --git a/media/capture/video/linux/video_capture_device_chromeos.cc b/media/capture/video/linux/video_capture_device_chromeos.cc
index 7003990ad5ee26c23d5dfc2445e6dc2e49cd5f37..8598889e32e4e771d67c1ab7448dd86d1de90b4f 100644
--- a/media/capture/video/linux/video_capture_device_chromeos.cc
+++ b/media/capture/video/linux/video_capture_device_chromeos.cc
@@ -152,8 +152,13 @@ void VideoCaptureDeviceChromeOS::SetRotation(int rotation) {
     //
     // Therefore, for back camera, we need to rotate (360 - |rotation|).
     rotation = (360 - rotation) % 360;
+  } else if (lens_facing_ == VideoFacingMode::MEDIA_VIDEO_FACING_NONE) {
+    // External cameras have lens_facing as MEDIA_VIDEO_FACING_NONE.
+    // We don't want to rotate the frame even if the device rotates.
+    rotation = 0;

[chfremer, 2017/03/20 16:32:47]

As a drive-by nit, I wonder if we could make things more obvious by introducing
a member |rotates_with_device_| and setting it to false for external cameras.
Otherwise, we run the risk that future developers may not be aware that setting
a MEDIA_VIDEO_FACING_NONE implies no rotation with the device.

[shenghao, 2017/03/21 06:06:31]

Done.

   }
-  // Take into account camera orientation w.r.t. the display.
+  // Take into account camera orientation w.r.t. the display. External cameras
+  // would have camera_orientation_ as 0.
   rotation = (rotation + camera_orientation_) % 360;
   VideoCaptureDeviceLinux::SetRotation(rotation);
 }