ui_test_utils::NavigateToURLBlockUntilNavigationsComplete can be raced
ui_test_utils::NavigateToURLBlockUntilNavigationsComplete can be raced

I found in some prefetching safe browsing tests that chrome went so
awesomely fast that events went by before NavigateToURL started
observing them.  And so I adapted the Windowed.... model to the
NavigationNotificationObserver, and use that now in NavigateToURL in
the current_tab case.

BUG=75507
TEST=see http://codereview.chromium.org/6334131/

Review URL: http://codereview.chromium.org/6662001

git-svn-id: http://src.chromium.org/svn/trunk/src@77638 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 620dc7b455c0113fc3c8e8929c7e6ccad04859fb
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser