SkPaintFilterCanvas skip-draw support

include/utils/SkPaintFilterCanvas.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPaintFilterCanvas_DEFINED
 #define SkPaintFilterCanvas_DEFINED
 
@@ skipping 30 matching lines @@
         kTextBlob_Type,
         kVertices_Type,
         kPatch_Type,
 
         kTypeCount
     };
 
 protected:
     /**
      *  Called with the paint that will be used to draw the specified type.
-     *  The implementation may modify the paint as they wish.
+     *  If not null, the implementation may modify the paint as they wish.
      *
-     *  Note: The base implementation calls onFilterPaint() for top-level/explicit paints only.
+     *  The result bool is used to determine whether the draw op is to be
+     *  executed (true) or skipped (false).
+     *
+     *  Note: The base implementation calls onFilter() for top-level/explicit paints only.
      *        To also filter encapsulated paints (e.g. SkPicture, SkTextBlob), clients may need to
      *        override the relevant methods (i.e. drawPicture, drawTextBlob).
      */
-    virtual void onFilterPaint(SkPaint* paint, Type type) const = 0;
+    virtual bool onFilter(SkPaint* paint, Type type) const {
+        if (paint) {

[f(malita), 2016/01/11 19:29:44]

Legacy/transient semantics.  To be converted to a pure virtual after Chromium
gets updated.

+            this->onFilterPaint(paint, type);
+        }
+        return true;
+    }
+
+    // DEPRECATED - do not use
+    virtual void onFilterPaint(SkPaint*, Type) const { }
 
     void onDrawPaint(const SkPaint&) override;
     void onDrawPoints(PointMode, size_t count, const SkPoint pts[], const SkPaint&) override;
     void onDrawRect(const SkRect&, const SkPaint&) override;
     void onDrawRRect(const SkRRect&, const SkPaint&) override;
     void onDrawDRRect(const SkRRect&, const SkRRect&, const SkPaint&) override;
     void onDrawOval(const SkRect&, const SkPaint&) override;
     void onDrawPath(const SkPath&, const SkPaint&) override;
     void onDrawBitmap(const SkBitmap&, SkScalar left, SkScalar top, const SkPaint*) override;
     void onDrawBitmapRect(const SkBitmap&, const SkRect* src, const SkRect& dst, const SkPaint*,
@@ skipping 24 matching lines @@
     void onDrawTextBlob(const SkTextBlob* blob, SkScalar x, SkScalar y,
                         const SkPaint& paint) override;
 
 private:
     class AutoPaintFilter;
 
     typedef SkNWayCanvas INHERITED;
 };
 
 #endif