DevTools: [Media Inspector] do not show MQ with equal dimensions

This patch makes media inspector to not show queries of the
same dimensions. These queries differ only in source locations, so the
"reveal in source code" in context menu now contains all the options.

R=dgozman@chromium.org, pfeldman@chromium.org

Review URL: https://codereview.chromium.org/342363004

git-svn-id: svn://svn.chromium.org/blink/trunk@176629 bbb929c8-8fbe-4397-9dbb-9b2b20218538