Handle empty title attribute tooltips.

Handle empty title attribute tooltips.

The spec tells us that if an element has a title attribute, its value
should be returned as its tooltip/advisory information:

  http://www.whatwg.org/specs/web-apps/current-work/#the-title-attribute

Align with how other browsers behave for <foo title> and return the
empty string rather than consult the parent element.

R=
BUG=399255
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180109

[sof, 2014-08-12 15:25:36]

Please take a look.

[abarth-chromium, 2014-08-12 17:36:14]

lgtm

[commit-bot: I haz the power, 2014-08-12 17:37:23]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sigbjornf@opera.com/462073003/1

[commit-bot: I haz the power, 2014-08-12 19:12:57]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/22320)

[commit-bot: I haz the power, 2014-08-12 19:40:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-12 19:40:13]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/22347)

[sof, 2014-08-12 21:24:58]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2014-08-12 21:26:35]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sigbjornf@opera.com/462073003/1

[commit-bot: I haz the power, 2014-08-12 22:35:34]

Change committed as 180109