Fix for a Mac build issue after r20846.

src/jsregexp.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 434 matching lines @@
 
   Handle<String> pattern(re->Pattern());
   pattern = String::Flatten(pattern);
   RegExpCompileData compile_data;
   FlatStringReader reader(isolate, pattern);
   if (!RegExpParser::ParseRegExp(&reader, flags.is_multiline(),
                                  &compile_data,
                                  &zone)) {
     // Throw an exception if we fail to parse the pattern.
     // THIS SHOULD NOT HAPPEN. We already pre-parsed it successfully once.
-    ThrowRegExpException(re,
-                         pattern,
-                         compile_data.error,
-                         "malformed_regexp");
+    USE(ThrowRegExpException(re,
+                             pattern,
+                             compile_data.error,
+                             "malformed_regexp"));
     return false;
   }
   RegExpEngine::CompilationResult result =
       RegExpEngine::Compile(&compile_data,
                             flags.is_ignore_case(),
                             flags.is_global(),
                             flags.is_multiline(),
                             pattern,
                             sample_subject,
                             is_ascii,
@@ skipping 5660 matching lines @@
   }
 
   return compiler.Assemble(&macro_assembler,
                            node,
                            data->capture_count,
                            pattern);
 }
 
 
 }}  // namespace v8::internal