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

Review URL: https://codereview.chromium.org/462073003

git-svn-id: svn://svn.chromium.org/blink/trunk@180109 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
tree: 1e7efa91b546f7f460a398f8e0d671e861953cc3
  1. third_party/