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/SkDashPathEffect.cpp b/src/effects/SkDashPathEffect.cpp
index f205977..58d746b 100644
--- a/src/effects/SkDashPathEffect.cpp
+++ b/src/effects/SkDashPathEffect.cpp
@@ -156,7 +156,7 @@
 };
 
 bool SkDashPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                  SkStrokeRec* rec) {
+                                  SkStrokeRec* rec) const {
     // we do nothing if the src wants to be filled, or if our dashlength is 0
     if (rec->isFillStyle() || fInitialDashLength < 0) {
         return false;