Fix flake in threaded CSSOM smooth scroll layout tests

Fix flake in threaded CSSOM smooth scroll layout tests

This removes waits and assertions about intermediate frames. In threaded
mode, there's no guarantee about the frequency of main-thread frames as
the animation progresses on the compositor thread. It's in fact possible
to have no main-thread frames until the animation finishes; this causes
tests that wait for an intermediate frame to time out, and causes tests
that assert that the end frame isn't reached to fail.

BUG=243871
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188898

[ajuma, 2015-01-22 20:58:32]

ajuma@chromium.org changed reviewers:
+ vollick@chromium.org

[Ian Vollick, 2015-01-23 17:03:36]

On 2015/01/22 20:58:37, ajuma wrote:

lgtm.

[ajuma, 2015-01-23 17:28:23]

The CQ bit was checked by ajuma@chromium.org

[commit-bot: I haz the power, 2015-01-23 17:28:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/872433002/1

[commit-bot: I haz the power, 2015-01-23 18:44:29]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188898