2014-02-24  Sharath Kamath  <s.kamath@samsung.com>

        Add switch for html_image extension in WebCL.

        Fixed #454

        Reviewed by Antonio.

        As per resolution in ::
        https://www.khronos.org/bugzilla/show_bug.cgi?id=1121.

        A extension is enabled at context level. i.e if a extension is
        enabled before context is created, the context will have those features
        enabled.
        So adding a switch() at WebCLContext, to make sure API of "WebCL_html_image"
        extension are available only with context that have this feature enabled.

        All test case for "WebCL_html_image" extension in test suite.

        * Modules/webcl/WebCLCommandQueue.cpp:
        (WebCore::WebCLCommandQueue::enqueueWriteBuffer):
        (WebCore::WebCLCommandQueue::enqueueWriteBufferRect):
        (WebCore::WebCLCommandQueue::enqueueReadBuffer):
        (WebCore::WebCLCommandQueue::enqueueReadImage):
        (WebCore::WebCLCommandQueue::enqueueReadBufferRect):
        (WebCore::WebCLCommandQueue::enqueueWriteImage):
        * Modules/webcl/WebCLContext.cpp:
        (WebCore::WebCLContext::WebCLContext):
        (WebCore::WebCLContext::isExtensionEnabled):
        (WebCore::WebCLContext::createBuffer):
        (WebCore::WebCLContext::createImage):
        * Modules/webcl/WebCLContext.h:
        * Modules/webcl/WebCLException.cpp:
        * Modules/webcl/WebCLException.h:
        * Modules/webcl/WebCLException.idl:
        * Modules/webcl/WebCLExtensionsAccessor.cpp:
        (WebCore::::enableExtension):
        (WebCore::::isEnabledExtension):
        * Modules/webcl/WebCLExtensionsAccessor.h:
        (WebCore::WebCLExtensionsAccessor::WebCLExtensionsAccessor):