Forward declare SkStrokeRec in SkPathEffect

Review URL: https://codereview.chromium.org/1312163008
diff --git a/bench/DashBench.cpp b/bench/DashBench.cpp
index 2653cdc..1003634 100644
--- a/bench/DashBench.cpp
+++ b/bench/DashBench.cpp
@@ -13,6 +13,7 @@
 #include "SkPath.h"
 #include "SkRandom.h"
 #include "SkString.h"
+#include "SkStrokeRec.h"
 #include "SkTDArray.h"