Redo r19140 with better efficiency.

test/cctest/test-parsing.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1780 matching lines @@
 
   const char* statement_data[] = {
     "mylabel: while(true) { break mylabel; }",
     "eval: while(true) { break eval; }",
     "arguments: while(true) { break arguments; }",
     NULL
   };
 
   RunParserSyncTest(context_data, statement_data, kSuccess);
 }
+
+
+TEST(ErrorsParenthesizedLabels) {
+  // Parenthesized identifiers shouldn't be recognized as labels.
+  const char* context_data[][2] = {
+    { "", ""},
+    { "function test_func() {", "}" },
+    { NULL, NULL }
+  };
+
+  const char* statement_data[] = {
+    "(mylabel): while(true) { break mylabel; }",
+    NULL
+  };
+
+  RunParserSyncTest(context_data, statement_data, kError);
+}
+
+
+TEST(NoErrorsParenthesizedDirectivePrologue) {
+  // Parenthesized directive prologue shouldn't be recognized.
+  const char* context_data[][2] = {
+    { "", ""},
+    { NULL, NULL }
+  };
+
+  const char* statement_data[] = {
+    "(\"use strict\"); var eval;",
+    NULL
+  };
+
+  RunParserSyncTest(context_data, statement_data, kSuccess);
+}