GitLab

Exposes several new states and attributes and fires new notifications
when the selection changes. Adds general-purpose implementations of
IUnknown and IEnumVARIANT to base/win/, which will be used in the future
as we remote ATL from accessibility code.

BUG=5027,98984
TEST=manual testing with JAWS and NVDA

Review URL: http://codereview.chromium.org/8588036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112870 0039d316-1c4b-4281-b951-d872f2087c98