Move GPU fences into sk_gpu_test

tools/gpu/gl/GLTestContext.h

Index: tools/gpu/gl/GLTestContext.h
diff --git a/tools/gpu/gl/GLTestContext.h b/tools/gpu/gl/GLTestContext.h
index efe9d8f100f7f36f9792ad26f1a83fd9fece5763..6a6b094ebb0eb906cf1175f8bdfc2dbf316e1291 100644
--- a/tools/gpu/gl/GLTestContext.h
+++ b/tools/gpu/gl/GLTestContext.h
@@ -65,15 +65,13 @@ protected:
     /*
      * Methods that sublcasses must call from their constructors and destructors.
      */
-    void init(const GrGLInterface *, SkGpuFenceSync * = NULL);
+    void init(const GrGLInterface *, FenceSync* = nullptr);
 
     void teardown() override;
 
     virtual GrGLFuncPtr onPlatformGetProcAddress(const char *) const = 0;
 
 private:
-    class GLFenceSync;  // SkGpuFenceSync implementation that uses the OpenGL functionality.
-
     /** Subclass provides the gl interface object if construction was
      *  successful. */
     SkAutoTUnref<const GrGLInterface> fGL;