[Video Capture Win] Fallback to DirectShow when MediaFoundation offers
no video format

Devices like Pinnacle Dazzle are listed in DirectShow with their video
formats while listed in MediaFoundation with no available video format
at all.

This makes the capture factory fallback to DirectShow implementation
when it contains at least one video format and its MediaFoundation
counterpart has none.

Bug: 862395
Change-Id: I5d02f97971d4cf98372e12bb96c0b7ad9cc6d9c3
Reviewed-on: https://chromium-review.googlesource.com/1137817
Commit-Queue: Christian Fremerey <chfremer@chromium.org>
Reviewed-by: Christian Fremerey <chfremer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575667}