Since HW codecs are not as well-behaved as SW codecs, we need a
way to disable the EXPECT_EQ's in the VideoProcessor integration tests
for the former. This CL introduces such an ability.
BUG=webrtc:6634
Review-Url: https://codereview.webrtc.org/2710913004
Cr-Commit-Position: refs/heads/master@{#17166}