Redo r19140 with better efficiency.

test/cctest/test-parsing.cc

Index: test/cctest/test-parsing.cc
diff --git a/test/cctest/test-parsing.cc b/test/cctest/test-parsing.cc
index 0106e5944f2a4db8ce44b7cc6a27f8997ceb8a9a..9768e30a55a6eac19f666e03f98a8a4c65f77d8d 100644
--- a/test/cctest/test-parsing.cc
+++ b/test/cctest/test-parsing.cc
@@ -1798,3 +1798,36 @@ TEST(NoErrorsIllegalWordsAsLabels) {
 
   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);
+}