gcc 4.6.1 -Wall -Werror fix.

ppapi/native_client/src/trusted/plugin/plugin.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifdef _MSC_VER
 // Do not warn about use of std::copy with raw pointers.
 #pragma warning(disable : 4996)
 #endif
 
 #include "native_client/src/trusted/plugin/plugin.h"
@@ skipping 1775 matching lines @@
                              plugin::FileDownloader*&,
                              pp::VarPrivate&);
 void Plugin::XYZZY(const nacl::string& url,
                            pp::VarPrivate js_callback) {
   UNREFERENCED_PARAMETER(url);
   UNREFERENCED_PARAMETER(js_callback);
   pp::CompletionCallback open_callback =
       callback_factory_.NewRequiredCallback(pmem,
           reinterpret_cast<plugin::FileDownloader*>(NULL),
           js_callback);
+  static_cast<void>(open_callback);
 }
 #endif  // HACK_FOR_MACOS_HANG_REMOVED
 
 
 void Plugin::ReportLoadSuccess(LengthComputable length_computable,
                                uint64_t loaded_bytes,
                                uint64_t total_bytes) {
   // Set the readyState attribute to indicate loaded.
   set_nacl_ready_state(DONE);
   // Inform JavaScript that loading was successful and is complete.
@@ skipping 196 matching lines @@
   std::string scheme = canonicalized.AsString().substr(comps.scheme.begin,
                                                        comps.scheme.len);
   if (scheme == kChromeExtensionUriScheme)
     return SCHEME_CHROME_EXTENSION;
   if (scheme == kDataUriScheme)
     return SCHEME_DATA;
   return SCHEME_OTHER;
 }
 
 }  // namespace plugin