More SaveFlags removal twiddling.

This is a follow up to https://codereview.chromium.org/338913002/. More
tweaks to allow migrating clients to the new API.

1) switch the shim call direction willSave(SaveFlags) -> willSave()
   (internal users are still using the former, so external overriders of
    the latter will not be notified otherwise - doh)
2) ensure willSave() stays visible in SkProxyCanvas (Chromium's
   TimingCanvas attempts to call it explicitly).

BUG=skia:2297
R=reed@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/334393008
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 738408b..a08e828 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -1201,9 +1201,9 @@
     };
 
     // Transitional, pending external clients cleanup.
-    virtual void willSave(SaveFlags) {}
+    virtual void willSave(SaveFlags) { this->willSave(); }
 
-    virtual void willSave() { this->willSave(kMatrixClip_SaveFlag); }
+    virtual void willSave() {}
     virtual SaveLayerStrategy willSaveLayer(const SkRect*, const SkPaint*, SaveFlags) {
         return kFullLayer_SaveLayerStrategy;
     }