Remove GrGpuTraceMarker hooks until we rethink the design

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index 566ae544591686d3133fc98f71c774fa405829f7..a111ee51851e58b34e437b4d5814241f9c470ad8 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -266,10 +266,6 @@ private:
 
     void clearStencil(GrRenderTarget* target) override  {}
 
-    void didAddGpuTraceMarker() override {}
-
-    void didRemoveGpuTraceMarker() override {}
-
     GrBackendObject createTestingOnlyBackendTexture(void* pixels, int w, int h,
                                                     GrPixelConfig config) const override {
         return 0;