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non-default orientation

Problem: When Windows tablet devices are locked in a non-default
orientation, the video capture stream is incorrectly rotated.

Cause: We always return a camera rotation of 0 when auto-rotation is
turned off. For devices locked in non-default orientations this leads
to incorrect camera rotation.

Fix: This change removes the IsAutoRotationEnabled() check inside
GetCameraRotation(). It also adds a new base::Optional<int> member
camera_rotation_ in video_capture_device_mf_win.cc and
video_capture_device_win.cc.

When a frame is received, if camera_rotation_ doesn't have a value OR
auto rotation is enabled, we call GetCameraRotation() and cache the
non-negative returned value in camera_rotation_. This enables us to
calculate and save the correct camera rotation when the first frame is
received. Further, if auto rotation is turned off during the capture
session, we'll be able to use the cached value to keep the
camera correctly rotated.

Testing: I added a test in video_capture_device_mf_win_unittest.cc to
verify that GetCameraRotation() is called and |camera_rotation_| is
populated when MFVideoCallback::OnSample() is invoked.

I also tested this change with both a naturally landscape and a
naturally portrait Windows tablet device locked in all possible
orientations. In each case the camera was correctly rotated.

Bug: 1134801
Change-Id: Ib1b6f1a4bb388b1390e5a257686c3b8a417a2a9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2447036Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Rahul Singh <rahsin@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#815223}