Make browser_accessibility fields private.

This will help with future refactoring so that we
can move data out of BrowserAccessibility and into
AXNode.

BUG=316726

Review URL: https://codereview.chromium.org/97813002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238625 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238625
Self-removing jar from owners in base

TBR=brettw

Review URL: https://codereview.chromium.org/102733004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238626 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238626