Slightly better text for "Please close all..." dialog if Chrome is the default browser on Windows 8.
BUG=123321
TEST=install Chrome on Windows 8, make it the default browser, relaunch it in metro mode, then try to uninstall. expect that the dialog telling you you can't uninstall mentions "Windows 8 mode" as a possible place to find an open Chrome window. now try again when Chrome isn't the default browser and expect to see the old text (no mention of Windows 8 mode).
Review URL: https://chromiumcodereview.appspot.com/
11066037
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160511 0039d316-1c4b-4281-b951-d872f2087c98