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
WebDocument::accessibilityObject should check axObjectCache

Document::axObjectCache() may return NULL, so it should be checked and
handled. This was reported by Huawei Technologies based on a stack trace
of an Android crash.

BUG=None

Review URL: https://codereview.chromium.org/563823002

git-svn-id: svn://svn.chromium.org/blink/trunk@182439 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Initialize members in TypeConversions test-only interface

Layout tests under MSAN FTW!

BUG=416415
R=earthdok@chromium.org
TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/593763002

git-svn-id: svn://svn.chromium.org/blink/trunk@182440 bbb929c8-8fbe-4397-9dbb-9b2b20218538