DevTools: [MQI] speedup Media Query Inspector rendering

MQI relied havily on computation of uiLocations, which is heavy and
in fact not really needed for rendering.

The patch moves to rawLocations which turns out to be way faster for the
rendering purposes. We still need uiLocations to handle context menu,
so they are processed and dedupped separately in context menu handler.

BUG=416408
R=pfeldman, dgozman

Review URL: https://codereview.chromium.org/589903005

git-svn-id: svn://svn.chromium.org/blink/trunk@182437 bbb929c8-8fbe-4397-9dbb-9b2b20218538