Win7: Show download progress in superbar.
Win7: Show download progress in superbar.

Use ITaskbarList3 interface to show progress bar when downloading items.

BUG=8039
TEST=Download a couple of files, notice it progress. Look at the screenshot in the main issue.

Review URL: http://codereview.chromium.org/944001

git-svn-id: http://src.chromium.org/svn/trunk/src@42066 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: bbe371da4a71a2f8eb57f7cca503fa5fe0584fc3
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