Use vertex attributes for dash effect in gpu

include/core/SkStrokeRec.h

Index: include/core/SkStrokeRec.h
diff --git a/include/core/SkStrokeRec.h b/include/core/SkStrokeRec.h
index 1e0ec880f7fafc8aa37f857be75443dc8f39e962..42bed8cbe701dfb2a28562b13cc1775dbca5cd9e 100644
--- a/include/core/SkStrokeRec.h
+++ b/include/core/SkStrokeRec.h
@@ -21,6 +21,7 @@ public:
     SkStrokeRec(InitStyle style);
 
     SkStrokeRec(const SkStrokeRec&);
+    SkStrokeRec(const SkPaint&, SkPaint::Style);
     explicit SkStrokeRec(const SkPaint&);
 
     enum Style {
@@ -90,6 +91,9 @@ public:
     }
 
 private:
+    void init(const SkPaint& paint, SkPaint::Style style);
+
+
     SkScalar        fWidth;
     SkScalar        fMiterLimit;
     SkPaint::Cap    fCap;