Fix accessibility in Windows x64 build.

The only fix needed was to cast the LPARAM to a DWORD when
handling WM_GETOBJECT in two places.

Also fixes and re-enables a bunch of Windows accessibility tests,
and deletes a couple of old disabled tests that aren't worth fixing.

BUG=179717,383240

Review URL: https://codereview.chromium.org/329863003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@277457 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed