Add jank metric for PrerenderManager::PeriodicCleanup.

Measure how long the call takes so we can correllate long stalls by platform
and see how frequent they are.

BUG=305419
TEST=none

Review URL: https://codereview.chromium.org/67813006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234948 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234948
Allows views of role "menu" to receive focus events.

This fix is not meant to redo the API, but simply to make it so ChromeVox can verbalize this important control. We should note the issues with this API in terms of indicating the caller's intent and some underlying assumptions made about what events can be fired on what roles.

BUG=318463
TEST=Ensure that the "apps" wrench menu gets announced by ChromeVox.

Review URL: https://codereview.chromium.org/71863003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234949 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234949