DevTools: [Console] get rid of ConsoleView._messageToViewMessage map

This patch gets rid of _messageToViewMessage map which stored viewMessages
for every console message. This map pretends to be lazy (via method
ConsoleView._viewMessageBy) but in fact it creates a viewMessage per (almost)
every incoming consoleMessage.

Review URL: https://codereview.chromium.org/243593002

git-svn-id: svn://svn.chromium.org/blink/trunk@172159 bbb929c8-8fbe-4397-9dbb-9b2b20218538