veatest: fix keyframe verification test.

veatest: fix keyframe verification test.

The test was not resilient against arbitrary pipeline depths and encode
delays. It was possible for the encode request to keep overwriting
keframe_requested_at_ faster than the deadline check by which we would've
failed if no keyframe was provided. Thus it was possible for the test to
always pass, even without getting any keyframes.

Simplify this by just checking that each keyframe arrives before
every keyframe_period_ + kMaxKeyframeDelay.

Also, some cleanup for fake encoder validator creation.

BUG=None
TEST=veatest --gtest_filter=ForceKeyframes*

Committed: https://crrev.com/4fc28962e2da8b3f278b952c55fefe10487db952
Cr-Commit-Position: refs/heads/master@{#317367}

[Pawel Osciak, 2015-02-20 10:44:23]

posciak@chromium.org changed reviewers:
+ scherkus@chromium.org, vmr@chromium.org

[Pawel Osciak, 2015-02-20 10:44:24]

ptal

[scherkus (not reviewing), 2015-02-20 17:48:51]

lgtm

[Pawel Osciak, 2015-02-20 19:00:31]

The CQ bit was checked by posciak@chromium.org

[commit-bot: I haz the power, 2015-02-20 19:01:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/942693003/1

[commit-bot: I haz the power, 2015-02-20 19:23:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-20 19:24:04]

Patchset 1 (id:??) landed as
https://crrev.com/4fc28962e2da8b3f278b952c55fefe10487db952
Cr-Commit-Position: refs/heads/master@{#317367}