Enable blend optimizations with instanced draws

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 5b24d8a3829d9cfc8993817cab5a8b82bcf6b665..2fb66804e007b78e3f1ecc2888c1fe4cc46a3053 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -23,6 +23,7 @@
 #include "glsl/GrGLSL.h"
 #include "glsl/GrGLSLCaps.h"
 #include "glsl/GrGLSLPLSPathRendering.h"
+#include "instanced/GLInstancedRendering.h"
 #include "SkMipMap.h"
 #include "SkPixmap.h"
 #include "SkStrokeRec.h"
@@ -46,6 +47,8 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
+using gr_instanced::InstancedRendering;
+using gr_instanced::GLInstancedRendering;
 
 static const GrGLenum gXfermodeEquation2Blend[] = {
     // Basic OpenGL blend equations.
@@ -475,6 +478,10 @@ void GrGLGpu::disconnect(DisconnectType type) {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+InstancedRendering* GrGLGpu::createInstancedRenderingIfSupported() {
+    return GLInstancedRendering::CreateIfSupported(this);
+}
+
 void GrGLGpu::onResetContext(uint32_t resetBits) {
     // we don't use the zb at all
     if (resetBits & kMisc_GrGLBackendState) {