rAc: Don't frantically resize the dialog when clicking "sign in".

BUG=313517

Review URL: https://codereview.chromium.org/53673004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232326 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232326