Don't delete npapi plugins copied into <(PRODUCT_DIR)/plugins during UI tests.
Don't delete npapi plugins copied into <(PRODUCT_DIR)/plugins
during UI tests.

The layout test plugin is copied over via a build step and needed
when running the layout tests.  If you run the UI tests before
the layout tests, the npapi layout test plugin is deleted and
causes layout tests to fail.  Seems like it's safe to keep the plugins
even after the UI tests end.

Review URL: http://codereview.chromium.org/3066033

git-svn-id: http://src.chromium.org/svn/trunk/src@54965 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 121f5e330128611ed5120c6c0dac5fe93a966bd2
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