DevTools: [Media Inspector] fix sorting of locations in Media Inspector

Media queries are not sorted inside sections related to their UI
location, which breaks precontract of method
MediaQueryInspector._squashAdjacentEqual.

Review URL: https://codereview.chromium.org/340383005

git-svn-id: svn://svn.chromium.org/blink/trunk@176738 bbb929c8-8fbe-4397-9dbb-9b2b20218538