Add class GrGLTextureRenderTarget for GL texture/rendertarget objects

src/gpu/GrOptDrawState.h

Index: src/gpu/GrOptDrawState.h
diff --git a/src/gpu/GrOptDrawState.h b/src/gpu/GrOptDrawState.h
index f495b8983a4e3c929ba32565c35809a42ae98399..c32294b14bb51ad445b82f1bc34fd9b749fffcc5 100644
--- a/src/gpu/GrOptDrawState.h
+++ b/src/gpu/GrOptDrawState.h
@@ -169,9 +169,7 @@ public:
      *
      * @return    The currently set render target.
      */
-    GrRenderTarget* getRenderTarget() const {
-        return static_cast<GrRenderTarget*>(fRenderTarget.getResource());
-    }
+    GrRenderTarget* getRenderTarget() const { return fRenderTarget.get(); }
 
     /// @}