DevTools: get rid of Element.prototype.removeMatchingStyleClasses

This method encourages className crafting and runs unexpectedly long.

BUG=316092

Review URL: https://codereview.chromium.org/466703002

git-svn-id: svn://svn.chromium.org/blink/trunk@180163 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [SSP] Implement adding new rule in user stylesheet

This patch implements an "add new rule" functionality to add a style rule in a user stylesheet. It is also possible to
add rule inside media query rules.

BUG=402461

Review URL: https://codereview.chromium.org/441873010

git-svn-id: svn://svn.chromium.org/blink/trunk@180164 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Do not push to frontend messages from worker while it is alive

BUG=

Review URL: https://codereview.chromium.org/466753002

git-svn-id: svn://svn.chromium.org/blink/trunk@180165 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Avoid rebaselining test results after changing InjectedScript.

TBR=vsevik

Review URL: https://codereview.chromium.org/468763004

git-svn-id: svn://svn.chromium.org/blink/trunk@180166 bbb929c8-8fbe-4397-9dbb-9b2b20218538