Add a test of invalidations with multiple RecalcStyle events

Add a test of invalidations with multiple RecalcStyle events

Multiple RecalcStyle events can occur in a single frame and we didn't
have a good test for associating invalidation events in this case. This
patch also does some minor cleanup of the style recalc test.

BUG=410701
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185423

[pdr., 2014-11-16 23:45:05]

pdr@chromium.org changed reviewers:
+ caseq@chromium.org, kouhei@chromium.org

[pdr., 2014-11-16 23:46:53]

In a work in progress patch I broke this tricky case. Adding a test so that
doesn't happen again.

[kouhei (in TOK), 2014-11-17 05:01:40]

lgtm

[pdr., 2014-11-17 05:26:27]

The CQ bit was checked by pdr@chromium.org

[commit-bot: I haz the power, 2014-11-17 05:27:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/727253002/1

[commit-bot: I haz the power, 2014-11-17 07:31:34]

Committed patchset #1 (id:1) as 185423