We DnD shouldn't provide text/html if it claims to provide text/text/plain;charset=utf-8.
We DnD shouldn't provide text/html if it claims to provide text/text/plain;charset=utf-8.

BUG=crosbug.com/2178
TEST=See http://code.google.com/p/chromium-os/issues/detail?id=2178

Review URL: http://codereview.chromium.org/1599023

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@44063 0039d316-1c4b-4281-b951-d872f2087c98

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