Add test configs for instanced rendering

src/gpu/GrGpu.cpp

Index: src/gpu/GrGpu.cpp
diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index 4cb96edd880144e69563f10b89485b6b8b88b5d2..7199b4d97694c62ba0555acf0a1b65939474459f 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -251,6 +251,11 @@ GrBuffer* GrGpu::createBuffer(size_t size, GrBufferType intendedType,
     return buffer;
 }
 
+gr_instanced::InstancedRendering* GrGpu::createInstancedRendering() {
+    SkASSERT(GrCaps::InstancedSupport::kNone != this->caps()->instancedSupport());
+    return this->onCreateInstancedRendering();
+}
+
 bool GrGpu::copySurface(GrSurface* dst,
                         GrSurface* src,
                         const SkIRect& srcRect,