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

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index eaf762d0e26972eaacd8ae48d8501a1cf22737f6..8842b7ab00d5ac3895ba7a845170e7531250f66e 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -100,6 +100,13 @@ public:
         return &this->glContext();
     }
 
+    void clearStencil(GrRenderTarget*) override;
+
+    void invalidateBoundRenderTarget() {
+        fHWBoundRenderTargetUniqueID = SK_InvalidUniqueID;
+    }
+
+
     GrBackendObject createTestingOnlyBackendTexture(void* pixels, int w, int h,
                                                     GrPixelConfig config) const override;
     bool isTestingOnlyBackendTexture(GrBackendObject id) const override;
@@ -123,9 +130,9 @@ private:
     GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) override;
     GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                               GrWrapOwnership) override;
-    bool createStencilAttachmentForRenderTarget(GrRenderTarget* rt, int width, int height) override;
-    bool attachStencilAttachmentToRenderTarget(GrStencilAttachment* sb,
-                                               GrRenderTarget* rt) override;
+    GrStencilAttachment* createStencilAttachmentForRenderTarget(const GrRenderTarget* rt,
+                                                                int width,
+                                                                int height) override;
     // Given a GrPixelConfig return the index into the stencil format array on GrGLCaps to a
     // compatible stencil format.
     int getCompatibleStencilIndex(GrPixelConfig config);
@@ -155,8 +162,6 @@ private:
                        const SkIRect& srcRect,
                        const SkIPoint& dstPoint) override;
 
-    void clearStencil(GrRenderTarget*) override;
-
     // binds texture unit in GL
     void setTextureUnit(int unitIdx);