Convert WebPluginInfo from wstring to string16

BUG=None
TEST=No behavioral change; plugins should continue to work.

Review URL: http://codereview.chromium.org/2866014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@50650 0039d316-1c4b-4281-b951-d872f2087c98
14 files changed