[Relanding 105659. This will re-cause failures in chrome_frame_net_tests, to be fixed in the next CL.]
Add a webRequest extension API permission, used to tell when an extension uses that API and therefore wants to delay startup. Use the "tabs" warning for it.
Also clean up the UserScriptListener, which never released requests individually and so doesn't need to track them individually either, and makes the RequestQueue handle bulk releases by its delegates instead.
BUG=99450
TEST=unit_tests.exe --gtest_filter=NetworkDelayListenerTest.*
Review URL: http://codereview.chromium.org/8205001TBR=pam@chromium.org
Review URL: http://codereview.chromium.org/8296017TBR=pam@chromium.org
Review URL: http://codereview.chromium.org/8308003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@105686 0039d316-1c4b-4281-b951-d872f2087c98