Reviewed by Alexey Proskuryakov.

        Add a key handling logging channel for WebKit2
        https://bugs.webkit.org/show_bug.cgi?id=61588
        
        Added a new LogKeyHandling channel, and logged some key events in WebPageProxy.
        I also fixed a misspelling of coalescing in a comment in WebPageProxy.cpp.

        * Platform/Logging.cpp:
        (WebKit::initializeLogChannelsIfNecessary): Initialize LogKeyHandling channel.
        * Platform/Logging.h: Added LogKeyHandling channel.

        * UIProcess/WebPageProxy.cpp: Fixed misspelling of coalescing in a comment.
        (WebKit::webKeyboardEventTypeString): Added to support logging.
        (WebKit::WebPageProxy::handleKeyboardEvent): Log the keyboard event.
        (WebKit::WebPageProxy::didReceiveEvent): Log the keyboard event.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@87509 268f45cc-cd09-0410-ab3c-d52691b4dbfc