Implement instanced rendering for simple shapes

src/gpu/GrDrawTarget.h

Index: src/gpu/GrDrawTarget.h
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index c863b455b36ed8ae630424daf503c179cdb8d6b1..94cee3c1f34dfd41ce91ba8d5805ad1d7738fd81 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -173,6 +173,11 @@ public:
 
     GrAuditTrail* getAuditTrail() const { return fAuditTrail; }
 
+    /**
+     * Gets the shape rendering object if it is supported on this platform.
+     */
+    GrInstancedRendering* instancedRendering() const { return fInstancedRendering; }
+
 private:
     friend class GrDrawingManager; // for resetFlag & TopoSortTraits
 
@@ -262,6 +267,8 @@ private:
     int                                         fMaxBatchLookback;
     int                                         fMaxBatchLookahead;
 
+    SkAutoTDelete<GrInstancedRendering>         fInstancedRendering;
+
     typedef SkRefCnt INHERITED;
 };