Move StringPiece into the base namespace. It is colliding

chrome/browser/extensions/external_pref_extension_provider.cc

 // Copyright (c) 2009 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/browser/extensions/external_pref_extension_provider.h"
 
 #include "app/app_paths.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
@@ skipping 40 matching lines @@
 
     FilePath::StringType external_crx;
     std::string external_version;
     if (!extension->GetString(kExternalCrx, &external_crx) ||
         !extension->GetString(kExternalVersion, &external_version)) {
       LOG(WARNING) << "Malformed extension dictionary for extension: "
                    << extension_id.c_str();
       continue;
     }
 
-    if (external_crx.find(FilePath::kParentDirectory) != StringPiece::npos) {
+    if (external_crx.find(FilePath::kParentDirectory) !=
+        base::StringPiece::npos) {
       LOG(WARNING) << "Path traversal not allowed in path: "
                    << external_crx.c_str();
       continue;
     }
 
     // See if it's an absolute path...
     FilePath path(external_crx);
     if (!path.IsAbsolute()) {
       // Try path as relative path from external extension dir.
       FilePath base_path;
@@ skipping 36 matching lines @@
     if (extensions) {
       if (!extensions->IsType(Value::TYPE_DICTIONARY)) {
         NOTREACHED() << L"Invalid json data";
       } else {
         dictionary.reset(static_cast<DictionaryValue*>(extensions));
       }
     }
   }
   prefs_.reset(dictionary.release());
 }