Add test configs for instanced rendering

tools/gpu/GrTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTest.h"
 
 #include "GrBatchAtlas.h"
@@ skipping 324 matching lines @@
     }
 
     GrRenderTarget* onWrapBackendTextureAsRenderTarget(const GrBackendTextureDesc&) override {
         return nullptr;
     }
 
     GrBuffer* onCreateBuffer(size_t, GrBufferType, GrAccessPattern, const void*) override {
         return nullptr;
     }
 
+    gr_instanced::InstancedRendering* onCreateInstancedRendering() override { return nullptr; }
+
     bool onReadPixels(GrSurface* surface,
                       int left, int top, int width, int height,
                       GrPixelConfig,
                       void* buffer,
                       size_t rowBytes) override {
         return false;
     }
 
     bool onWritePixels(GrSurface* surface,
                        int left, int top, int width, int height,
@@ skipping 41 matching lines @@
     SkASSERT(nullptr == fGpu);
     fGpu = new MockGpu(this, options);
     SkASSERT(fGpu);
     this->initCommon(options);
 
     // We delete these because we want to test the cache starting with zero resources. Also, none of
     // these objects are required for any of tests that use this context. TODO: make stop allocating
     // resources in the buffer pools.
     fDrawingManager->abandon();
 }