Fix windows accessibility tree traversal.

Some interfaces were traversing the whole tree rather than
only the part of the tree we intend to expose to that
platform. This needs some cleanup to make it harder for
bugs like this to occur, but first, this fixes the current
implementation.

BUG=320100

Review URL: https://codereview.chromium.org/68503020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235545 0039d316-1c4b-4281-b951-d872f2087c98
Moved the notification 'expand' logic to NotificationView.

Also moved the ControlButton
into separate file and renamed it into PaddedButton.
This is to make MessageView more generic (placeholder with close button) so
it can serve as a base class for 'synthetic notifications'.

BUG=none

Review URL: https://codereview.chromium.org/73553002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235546 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235545
SVN changes up to revision 235546
Remove unused base/win/extra_sdk_defines.h.

The definitions in this file are unused.

BUG=319039
TEST=No build breaks, no regressions.
R=tommi@chromium.org,sky@chromium.org

Review URL: https://codereview.chromium.org/73563007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235547 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235547