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In the short term, this addresses the issue of messages that are too long
to fit in the dialog - the window will extend outside the dialog. In the
long run, this also prepares for further changes around the error bubble
that do require the BaseBubble machinery.

R=rsesek@chromium.org
BUG=308200

Review URL: https://codereview.chromium.org/49063012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233458 0039d316-1c4b-4281-b951-d872f2087c98