Add a background timing thread to kilobench

include/gpu/gl/SkGLContext.h

Index: include/gpu/gl/SkGLContext.h
diff --git a/include/gpu/gl/SkGLContext.h b/include/gpu/gl/SkGLContext.h
index 992edf4efd2631f8ae540e7c0bf19480d7ceb518..ddf5dc080a113ec648e9b94409184e22eda21610 100644
--- a/include/gpu/gl/SkGLContext.h
+++ b/include/gpu/gl/SkGLContext.h
@@ -85,6 +85,11 @@ public:
 
     class GLFenceSync;  // SkGpuFenceSync implementation that uses the OpenGL functionality.
 
+    /*
+     * returns the fencesync object owned by this SkGLContext
+     */
+    SkGpuFenceSync* fenceSync() { return fFenceSync.get(); }
+
 protected:
     SkGLContext();