gitignore: Add /chrome/browser/extensions/default_extensions/chromeos
gitignore: Add /chrome/browser/extensions/default_extensions/chromeos

BUG=none
TEST="git status"
TBR=skerner@chromium.org

Review URL: http://codereview.chromium.org/3290017

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@58918 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