Move StringPiece into the base namespace. It is colliding

chrome/tools/mac_helpers/infoplist_strings_util.mm

 // 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.
 
 // Helper tool that is built and run during a build to pull strings from
 // the GRD files and generate the InfoPlist.strings files needed for
 // Mac OS X app bundles.
 
 #import <Foundation/Foundation.h>
 
@@ skipping 58 matching lines @@
   }
 
   return resource_pack;
 }
 
 NSString* LoadStringFromDataPack(base::DataPack* data_pack,
                                  const char* data_pack_lang,
                                  uint32_t resource_id,
                                  const char* resource_id_str) {
   NSString* result = nil;
-  StringPiece data;
+  base::StringPiece data;
   if (data_pack->Get(resource_id, &data)) {
     // Data pack encodes strings as UTF16.
     result =
         [[[NSString alloc] initWithBytes:data.data()
                                   length:data.length()
                                 encoding:NSUTF16LittleEndianStringEncoding]
          autorelease];
   }
   if (!result) {
     fprintf(stderr, "ERROR: failed to load string %s for lang %s\n",
@@ skipping 201 matching lines @@
         [output_path stringByAppendingPathComponent:@"InfoPlist.strings"];
     if (![strings_file_contents_utf8 writeToFile:output_path
                                       atomically:YES]) {
       fprintf(stderr, "ERROR: Failed to write out '%s'\n",
               [output_path UTF8String]);
       exit(1);
     }
   }
   return 0;
 }