DevTools: Extract dumpConsoleTableMessage for future testing.

Extract the method, invoke it from InspectorTest.dumpConsoleMessages.

BUG=
R=pfeldman,vsevik

Review URL: https://codereview.chromium.org/25583006

git-svn-id: svn://svn.chromium.org/blink/trunk@158740 bbb929c8-8fbe-4397-9dbb-9b2b20218538