Never force a max dialog height of less than 200 pixels

Some dialogs liks chrome://settings/clearBrowserData and
chrome://settings/resetProfileSettings look really bad if the browser window
has a very small height. This CL ensures that the dialog can always occupy 200
vertical pixels.

BUG=329792

Review URL: https://codereview.chromium.org/104713012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243295 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243295