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

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index 4e697ff655485589e560a2cd1da8e4e38eebd1b2..8d6208de7908fd3657cbdfc067c250f40f516646 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -255,12 +255,10 @@ private:
 
     void onResolveRenderTarget(GrRenderTarget* target) override { return; }
 
-    bool createStencilAttachmentForRenderTarget(GrRenderTarget*, int width, int height) override {
-        return false;
-    }
-
-    bool attachStencilAttachmentToRenderTarget(GrStencilAttachment*, GrRenderTarget*) override {
-        return false;
+    GrStencilAttachment* createStencilAttachmentForRenderTarget(const GrRenderTarget*,
+                                                                int width,
+                                                                int height) override {
+        return nullptr;
     }
 
     void clearStencil(GrRenderTarget* target) override  {}