Create SkLayerRasterizer w/o destroying Builder.

include/effects/SkLayerRasterizer.h

Index: include/effects/SkLayerRasterizer.h
diff --git a/include/effects/SkLayerRasterizer.h b/include/effects/SkLayerRasterizer.h
index fdfb179cb6bab604188c2f20b12f74697e29b757..fc21a7cd18884d72efcf3bbe95b5245dc408fa21 100644
--- a/include/effects/SkLayerRasterizer.h
+++ b/include/effects/SkLayerRasterizer.h
@@ -39,10 +39,26 @@ public:
 
         /**
           *  Pass queue of layers on to newly created layer rasterizer and return it. The builder
-          *  cannot be used any more after calling this function.
+          *  *cannot* be used any more after calling this function.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
           */
         SkLayerRasterizer* detachRasterizer();
 
+        /**
+          *  Create and return a new immutable SkLayerRasterizer that contains a shapshot of the
+          *  layers that were added to the Builder, without modifying the Builder. The Builder
+          *  *may* be used after calling this function. It will continue to hold any layers
+          *  previously added, so consecutive calls to this function will return identical objects,
+          *  and objects returned by future calls to this function contain all the layers in
+          *  previously returned objects.
+          *
+          *  Future calls to addLayer will not affect rasterizers previously returned by this call.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
+          */
+        SkLayerRasterizer* snapshotRasterizer() const;

[reed1, 2014/04/10 20:16:42]

can this guy be const? Does it have to be? I'd be fine if it wasn't, but I leave
that to you.

[scroggo, 2014/04/10 20:21:37]

As stated in person, it can, but does not have to be const. I like declaring it
const because the whole point of this function is that it returns a layer
rasterizer without modifying the builder.

+
     private:
         SkDeque* fLayers;
     };
@@ -86,6 +102,8 @@ private:
 
     static SkDeque* ReadLayers(SkReadBuffer& buffer);
 
+    friend class LayerRasterizerTester;
+
     typedef SkRasterizer INHERITED;
 };