Remove obsolete String + code

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 8799)
+++ runtime/vm/parser.cc	(working copy)
@@ -26,7 +26,6 @@
 DEFINE_FLAG(bool, trace_parser, false, "Trace parser operations.");
 DEFINE_FLAG(bool, warning_as_error, false, "Treat warnings as errors.");
 DEFINE_FLAG(bool, silent_warnings, false, "Silence warnings.");
-DEFINE_FLAG(bool, allow_string_plus, false, "Allow + operator on strings.");
 
 static void CheckedModeHandler(bool value) {
   FLAG_enable_asserts = value;
@@ -5938,29 +5937,8 @@
             op_pos, op_kind, left_operand, right_operand);
         break;  // Equality and relational operators cannot be chained.
       } else {
-        StringConcatNode* str_concat = NULL;
-        if (op_kind == Token::kADD) {
-          if (left_operand->IsLiteralNode()) {
-            LiteralNode* lit = left_operand->AsLiteralNode();
-            if (lit->literal().IsString()) {
-              if (FLAG_allow_string_plus) {
-                str_concat = new StringConcatNode(lit->token_index());
-                str_concat->AddExpr(lit);
-              } else {
-                ErrorMsg(op_pos, "operator + on strings no longer allowed");
-              }
-            }
-          } else if (left_operand->IsStringConcatNode()) {
-            str_concat = left_operand->AsStringConcatNode();
-          }
-        }
-        if (str_concat != NULL) {
-          str_concat->AddExpr(right_operand);
-          left_operand = str_concat;
-        } else {
-          left_operand = OptimizeBinaryOpNode(
-              op_pos, op_kind, left_operand, right_operand);
-        }
+        left_operand = OptimizeBinaryOpNode(
+            op_pos, op_kind, left_operand, right_operand);
       }
     }
     current_preced--;