2014-02-25  Sharath Kamath  <s.kamath@samsung.com>

        [Part-2] Cache the enabled extensions when we createContext.

        Fixed #454

        Reviewed by Antonio.

        Pending work for commit 71d6b00c573f64e1e28838f791032dea3d87d853.
        We need to cache the enabled extensions in the context.
        Any extension enabled after context creation will not enable the features
        for the old context.

        Also change signature of isExtensionEnabled() to take raw pointer.

        * Modules/webcl/WebCLContext.cpp:
        (WebCore::WebCLContext::WebCLContext):
        (WebCore::WebCLContext::getEnabledExtensions):
        * Modules/webcl/WebCLContext.h: