2014-02-14  Sharath Kamath  <s.kamath@samsung.com>

        Add slicePitch to enqueueReadBufferRect with

        Fixed #451

        Reviewed by Antonio.

        Mismatch with specification.
        http://www.khronos.org/registry/webcl/extensions/WEBCL_html_image/

        Test cases in conformance/extension/WEBCL_html_image/cl_commandQueue_enqueueReadBufferRect_with_HTMLCanvasElement.html

        * Modules/webcl/WebCLCommandQueue.cpp:
        (WebCore::WebCLCommandQueue::enqueueReadBufferRect):
        * Modules/webcl/WebCLCommandQueue.h:
        * Modules/webcl/WebCLCommandQueue.idl: