Add Layout Test for WebCLProgram::build with optional WebCLCallback

        Add Layout Test for WebCLProgram::build with optional WebCLCallback.

        Reviewed by NOBODY (OOPS!).

        * webcl/tests/webcl-test-program-build-with-callback-expected.txt: Added.
        * webcl/tests/webcl-test-program-build-with-callback.html: Added.