In GrShape detect that stroked axis-aligned lines are rrects.

src/gpu/GrStyle.h

Index: src/gpu/GrStyle.h
diff --git a/src/gpu/GrStyle.h b/src/gpu/GrStyle.h
index 326f800442c9d2061102ffa2bcfc89b25a552ffc..9091166fe1b5b3382ffddf802db8d8fb2471b905 100644
--- a/src/gpu/GrStyle.h
+++ b/src/gpu/GrStyle.h
@@ -51,7 +51,9 @@ public:
      */
     enum KeyFlags {
         // The shape being styled has no open contours.
-        kClosed_KeyFlag = 0x1
+        kClosed_KeyFlag = 0x1,
+        // The shape being styled doesn't have any joins and so isn't affected by join type.
+        kNoJoins_KeyFlag = 0x2
     };
 
     /**