2014-05-19  Shilpa Shri  <shilpa.shri@samsung.com>

        Align getWorkGroupInfo signature with OpenCL

        Fixed #525

        Reviewed by Antonio.

        Making 'device' argument of getWorkGroupInfo(device, name)
        as nullable if there is only 1 device associated with kernel.

        Conformance tests:
        conformance/bindingTesting/fetchInfo/cl_kernel_getWorkGroupInfo.html

        * Modules/webcl/WebCLKernel.cpp:
        (WebCore::WebCLKernel::getWorkGroupInfo):
        * Modules/webcl/WebCLKernel.idl:
        * platform/ComputeKernel.h:
        (WebCore::ComputeKernel::getWorkGroupInfo):