Remove source line tracking from MediaList and related DevTools code

Now that the DevTools can track the source range related to CSSMedia,
MediaList::m_sourceLine and CSS.CSSMedia.sourceLine are no longer needed.

R=pfeldman, vsevik, yurys@chromium.org
BUG=none

Review URL: https://chromiumcodereview.appspot.com/17112022

git-svn-id: svn://svn.chromium.org/blink/trunk@152716 bbb929c8-8fbe-4397-9dbb-9b2b20218538
8 files changed