[DevTools] NetworkPanel: add option to see/copy long WS frame messages.

WS frames are not wrapped anymore.

To see full message content user can hover massage and look at popup.
Also added context menu to copy message to clipboard.

BUG=286419

Review URL: https://chromiumcodereview.appspot.com/24090002

git-svn-id: svn://svn.chromium.org/blink/trunk@157688 bbb929c8-8fbe-4397-9dbb-9b2b20218538