Builder class for SkLayerRasterizer.

include/effects/SkLayerRasterizer.h

Index: include/effects/SkLayerRasterizer.h
diff --git a/include/effects/SkLayerRasterizer.h b/include/effects/SkLayerRasterizer.h
index be81a2ba3defd30f273788967bfb95481ec50d51..fdfb179cb6bab604188c2f20b12f74697e29b757 100644
--- a/include/effects/SkLayerRasterizer.h
+++ b/include/effects/SkLayerRasterizer.h
@@ -18,9 +18,36 @@ class SkPaint;
 
 class SK_API SkLayerRasterizer : public SkRasterizer {
 public:
-            SkLayerRasterizer();
     virtual ~SkLayerRasterizer();
 
+    class SK_API Builder {
+    public:
+        Builder();
+        ~Builder();
+
+        void addLayer(const SkPaint& paint) {
+            this->addLayer(paint, 0, 0);
+        }
+
+        /**
+          *  Add a new layer (above any previous layers) to the rasterizer.
+          *  The layer will extract those fields that affect the mask from
+          *  the specified paint, but will not retain a reference to the paint
+          *  object itself, so it may be reused without danger of side-effects.
+          */
+        void addLayer(const SkPaint& paint, SkScalar dx, SkScalar dy);
+
+        /**
+          *  Pass queue of layers on to newly created layer rasterizer and return it. The builder
+          *  cannot be used any more after calling this function.
+          */
+        SkLayerRasterizer* detachRasterizer();
+
+    private:
+        SkDeque* fLayers;
+    };
+
+#ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
     void addLayer(const SkPaint& paint) {
         this->addLayer(paint, 0, 0);
     }
@@ -31,10 +58,12 @@ public:
         object itself, so it may be reused without danger of side-effects.
     */
     void addLayer(const SkPaint& paint, SkScalar dx, SkScalar dy);
+#endif
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLayerRasterizer)
 
 protected:
+    SkLayerRasterizer(SkDeque* layers);
     SkLayerRasterizer(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
@@ -43,8 +72,19 @@ protected:
                              const SkIRect* clipBounds,
                              SkMask* mask, SkMask::CreateMode mode) const;
 
+#ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
+public:
+#endif
+    SkLayerRasterizer();
+
 private:
-    SkDeque fLayers;
+#ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
+    SkDeque* fLayers;
+#else
+    const SkDeque* const fLayers;
+#endif
+
+    static SkDeque* ReadLayers(SkReadBuffer& buffer);
 
     typedef SkRasterizer INHERITED;
 };