Check for xfer barriers in GrBatch, auto-issue barriers in GrGpu

Review URL: https://codereview.chromium.org/1287973003
diff --git a/src/gpu/GrTessellatingPathRenderer.cpp b/src/gpu/GrTessellatingPathRenderer.cpp
index 4d23217..4809521 100644
--- a/src/gpu/GrTessellatingPathRenderer.cpp
+++ b/src/gpu/GrTessellatingPathRenderer.cpp
@@ -1576,9 +1576,7 @@
         batchTarget->draw(vertices);
     }
 
-    bool onCombineIfPossible(GrBatch*) override {
-        return false;
-    }
+    bool onCombineIfPossible(GrBatch*, const GrCaps&) override { return false; }
 
 private:
     TessellatingPathBatch(const GrColor& color,