Fix warning (struct forward-declared as class).

Review URL:  http://codereview.appspot.com/164061


git-svn-id: http://skia.googlecode.com/svn/trunk@451 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkEdgeBuilder.h b/src/core/SkEdgeBuilder.h
index e9ed519..767735f 100644
--- a/src/core/SkEdgeBuilder.h
+++ b/src/core/SkEdgeBuilder.h
@@ -5,7 +5,7 @@
 #include "SkRect.h"
 #include "SkTDArray.h"
 
-class SkEdge;
+struct SkEdge;
 class SkEdgeClipper;
 class SkPath;