change all interfaces for SkRasterizer to const, in preparation for marking it
as immutable/re-entrant safe.
Review URL: https://codereview.appspot.com/6936064

git-svn-id: http://skia.googlecode.com/svn/trunk@6878 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkLayerRasterizer.cpp b/src/effects/SkLayerRasterizer.cpp
index 7365e12..ea5808c 100644
--- a/src/effects/SkLayerRasterizer.cpp
+++ b/src/effects/SkLayerRasterizer.cpp
@@ -87,7 +87,7 @@
 
 bool SkLayerRasterizer::onRasterize(const SkPath& path, const SkMatrix& matrix,
                                     const SkIRect* clipBounds,
-                                    SkMask* mask, SkMask::CreateMode mode) {
+                                    SkMask* mask, SkMask::CreateMode mode) const {
     if (fLayers.empty()) {
         return false;
     }