In Clear11, use ID3D11DeviceContext1::ClearView when appropriate

Change-Id: I8d9054b5582cfe78beaff07146adc73b4716eaf9
Reviewed-on: https://chromium-review.googlesource.com/233680
Tested-by: Austin Kinross <aukinros@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>