2014-01-24  Sharath Kamath  <s.kamath@samsung.com>

        Incorrect event hadnling in WebCLEvent related class.

        Issue #431

        Reviewed by Antonio.

        Mainly fixes minor issues to assure implementation is in par with
        specification and conformance.
        Does not change behaviour with WebCLUserEvent by these API's.

        Conformance test cases:
        [https://github.com/SRA-SiliconValley/webkit-webcl-conformance]
        conformance/bindingTesting/eventsAndCallbacks/cl_webcl_waitForEvents.html
        conformance/bindingTesting/queues/cl_commandQueue_enqueueWaitForEvents.html
        conformance/bindingTesting/queues/cl_commandQueue_enqueueBarrier.html

        * Modules/webcl/WebCL.cpp:
        (WebCore::WebCL::waitForEvents):
        * Modules/webcl/WebCLCommandQueue.cpp:
        (WebCore::WebCLCommandQueue::enqueueMarker):