change signature for virtual related to saveLayer, passing SaveLayerRec

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1533953002

NOTREECHECKS=True

Review URL: https://codereview.chromium.org/1533953002
diff --git a/src/utils/SkNWayCanvas.cpp b/src/utils/SkNWayCanvas.cpp
index 05909a3..4f60ca3 100644
--- a/src/utils/SkNWayCanvas.cpp
+++ b/src/utils/SkNWayCanvas.cpp
@@ -66,14 +66,13 @@
     this->INHERITED::willSave();
 }
 
-SkCanvas::SaveLayerStrategy SkNWayCanvas::willSaveLayer(const SkRect* bounds, const SkPaint* paint,
-                                                        SaveFlags flags) {
+SkCanvas::SaveLayerStrategy SkNWayCanvas::getSaveLayerStrategy(const SaveLayerRec& rec) {
     Iter iter(fList);
     while (iter.next()) {
-        iter->saveLayer(bounds, paint, flags);
+        iter->saveLayer(rec);
     }
 
-    this->INHERITED::willSaveLayer(bounds, paint, flags);
+    this->INHERITED::getSaveLayerStrategy(rec);
     // No need for a layer.
     return kNoLayer_SaveLayerStrategy;
 }