Enable custom MIME types in web copy/paste.

Also fixes a leak that was accidentally introduced in http://src.chromium.org/viewvc/chrome?view=rev&revision=113018.

BUG=31037,106472
TEST=manual testing

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113040

Review URL: http://codereview.chromium.org/8802004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113064 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed