Fix DIR_SOURCE_ROOT for WebKit checkouts on linux
Fix DIR_SOURCE_ROOT for WebKit checkouts on linux

There's a hardcoded path fixup for base::DIR_SOURCE_ROOT for WebKit-only checkouts that wasn't
updated when the WebKit/chromium directory moved under Source/ a few weeks ago.

BUG=
TEST=

Review URL: http://codereview.chromium.org/6334035

git-svn-id: http://src.chromium.org/svn/trunk/src@73371 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: d3c0e4a82c62fe390fcb2839a68243b33e631d82
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