Move some of the adding stencil attachment logic of Gpu and into Render Target.

src/gpu/gl/GrGLRenderTarget.h

Index: src/gpu/gl/GrGLRenderTarget.h
diff --git a/src/gpu/gl/GrGLRenderTarget.h b/src/gpu/gl/GrGLRenderTarget.h
index 1e6dc7f767edd9a738415f7b9b2d69da50e67263..89541eb0ae60330775c5d488e33bc1f6be8a6054 100644
--- a/src/gpu/gl/GrGLRenderTarget.h
+++ b/src/gpu/gl/GrGLRenderTarget.h
@@ -78,6 +78,9 @@ protected:
     size_t onGpuMemorySize() const override;
 
 private:
+    GrGLGpu* getGLGpu() const;
+    bool completeStencilAttachment() override;
+
     GrGLuint    fRTFBOID;
     GrGLuint    fTexFBOID;
     GrGLuint    fMSColorRenderbufferID;