2013-01-24  Sharath Kamath  <kamath.sharath@gmail.com>

        WebCLCommandQueue check pointers to avoid bad memory access.
        Issue #93

        Reviewed by NOBODY (OOPS!).

        Error can be thrown by WebCL or a null passed to OpenCL.
        If OpenCL needs a non-null value it will throw a exception which will
        be handled by WebCL.

        No new tests (OOPS!).

        * Modules/webcl/WebCLCommandQueue.cpp:
        (WebCore::WebCLCommandQueue::enqueueWriteBuffer):
        (WebCore::WebCLCommandQueue::enqueueWriteBufferRect):
        (WebCore::WebCLCommandQueue::enqueueReadImage):
        (WebCore::WebCLCommandQueue::enqueueReadBuffer):
        (WebCore::WebCLCommandQueue::enqueueReadBufferRect):
        (WebCore::WebCLCommandQueue::enqueueNDRangeKernel):
        (WebCore::WebCLCommandQueue::enqueueWriteImage):
        (WebCore::WebCLCommandQueue::enqueueCopyImage):
        (WebCore::WebCLCommandQueue::enqueueCopyImageToBuffer):
        (WebCore::WebCLCommandQueue::enqueueCopyBufferToImage):
        (WebCore::WebCLCommandQueue::enqueueCopyBufferRect):