Revert of Do the early return when role is different than UnknownRole

Revert of Do the early return when role is different than UnknownRole (patchset #1 id:1 of https://codereview.chromium.org/756823004/)

Reason for revert:
Two Nexus 4 tests started crashing after this change:

ast/animation/request-animation-frame-callback-id.html
svg/canvas/canvas-pattern-svg.html

See eg

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fanimation%2Frequest-animation-frame-callback-id.html&testType=layout-tests

First failure is here:

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Android%20%28Nexus4%29/builds/23692

However the Nexus 4 bot is exhibiting other problems from build 23691 that might be related. So this is a speculative rollout.

Original issue's description:
> Do the early return when role is different than UnknownRole
> 
> We do not need to call ariaRoleAttribute() to check whether current role
> is different than UnknownRole. Just check m_ariaRole instead.
> 
> BUG=
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186527

TBR=dmazzoni@chromium.org,k.czech@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186566

[dominicc (has gone to gerrit), 2014-12-05 05:00:30]

Created Revert of Do the early return when role is different than UnknownRole

[commit-bot: I haz the power, 2014-12-05 05:03:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/773213003/1

[commit-bot: I haz the power, 2014-12-05 05:04:00]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=186566