[DevTools] Always show context menu for console messages.

On Mac, on right-click first text is selected under cursor
and then contextmenu handler fire with selection already set. That made
context menu very hard to use in console for Mac users.

BUG=330159

Review URL: https://codereview.chromium.org/117553004

git-svn-id: svn://svn.chromium.org/blink/trunk@164973 bbb929c8-8fbe-4397-9dbb-9b2b20218538