2013-03-27  Sharath Kamath  <kamath.sharath@gmail.com>

        ComputeContext::createImage2D throws exception on OpenCL1.2
        Issue #201

        As c style structures do not get initialised with 0, we need
        to initialize cl_image_desc object to default values.

        Reviewed by Antonio.

        No new tests (OOPS!).

        * platform/opencl/ComputeContextCL.cpp:
        (WebCore::ComputeContext::createImage2D): Initialize all values to 0.
        Explicit values can be set individually as need arises.