[crankshaft] Fix string addition to check for max length of cons string.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index 1ddc4a80b60b51239e74ccc0b4d4930f62c0aa89..3f2b9d5dcca403d712caaba242da09c6f1b8d2c1 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -2241,6 +2241,9 @@ HValue* HGraphBuilder::BuildUncheckedStringAdd(
   IfBuilder if_createcons(this);
   if_createcons.If<HCompareNumericAndBranch>(
       length, Add<HConstant>(ConsString::kMinLength), Token::GTE);
+  if_createcons.And();
+  if_createcons.If<HCompareNumericAndBranch>(
+      length, Add<HConstant>(ConsString::kMaxLength), Token::LTE);
   if_createcons.Then();
   {
     // Create a cons string.