Reduce severity of alert level when extension installation fails.
Reduce severity of alert level when extension installation fails.

BUG=19907
TEST=as described in bug
Review URL: http://codereview.chromium.org/204034

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@26366 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser