Use base namespace for string16 in chrome/renderer.

chrome/renderer/spellchecker/custom_dictionary_engine.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/renderer/spellchecker/custom_dictionary_engine.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 
 CustomDictionaryEngine::CustomDictionaryEngine() {
@@ skipping 23 matching lines @@
     dictionary_.insert(UTF8ToUTF16(*it));
   }
   for (std::vector<std::string>::const_iterator it = words_removed.begin();
        it != words_removed.end();
        ++it) {
     dictionary_.erase(UTF8ToUTF16(*it));
   }
 }
 
 bool CustomDictionaryEngine::SpellCheckWord(
-    const string16& text,
+    const base::string16& text,
     int misspelling_start,
     int misspelling_len) {
   // The text to be checked is empty on OSX(async) right now.
   // TODO(groby): Fix as part of async hook-up. (http://crbug.com/178241)
   return
       misspelling_start >= 0 &&
       misspelling_len > 0 &&
       size_t(misspelling_start + misspelling_len) <= text.length() &&
       dictionary_.count(text.substr(misspelling_start, misspelling_len)) > 0;
 }