Fix incorrect merge of r12822 into 3.13 branch.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index d3526a8feb205ec664e1493c73247da3133da5a3..c5c9eaf26c32722cd130e1287e99d35294e59992 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -4712,6 +4712,7 @@ class HStringAdd: public HBinaryOperation {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
+    SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
@@ -4795,7 +4796,6 @@ class HStringLength: public HUnaryOperation {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
-    SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {