change all patheffect methods to const, in preparation for marking its
subclasses as immutable/re-entrant safe.
Review URL: https://codereview.appspot.com/6949071

git-svn-id: http://skia.googlecode.com/svn/trunk@6877 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkDiscretePathEffect.cpp b/src/effects/SkDiscretePathEffect.cpp
index 8a7c307..a936be9 100644
--- a/src/effects/SkDiscretePathEffect.cpp
+++ b/src/effects/SkDiscretePathEffect.cpp
@@ -26,7 +26,7 @@
 }
 
 bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                      SkStrokeRec* rec) {
+                                      SkStrokeRec* rec) const {
     bool doFill = rec->isFillStyle();
 
     SkPathMeasure   meas(src, doFill);