Update some uses of UTF conversions in chrome/browser to use the base:: namespace.

chrome/browser/ui/cocoa/autofill/autofill_details_container_unittest.mm

 // Copyright (c) 2013 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.
 
 #import "chrome/browser/ui/cocoa/autofill/autofill_details_container.h"
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/strings/utf_string_conversions.h"
 #import "chrome/browser/ui/cocoa/autofill/autofill_section_container.h"
 #include "chrome/browser/ui/autofill/mock_autofill_dialog_view_delegate.h"
@@ skipping 38 matching lines @@
   EXPECT_CALL(delegate_, InputsAreValid(_, _))
       .Times(3)
       .WillOnce(Return(validity))
       .WillOnce(Return(validity))
       .WillOnce(Return(validity));
 
   EXPECT_TRUE([container_ validate]);
 
   ValidityMessages invalid;
   invalid.Set(ADDRESS_HOME_ZIP,
-              ValidityMessage(ASCIIToUTF16("Some error message"), false));
+              ValidityMessage(base::ASCIIToUTF16("Some error message"), false));
 
   EXPECT_CALL(delegate_, InputsAreValid(_, _))
       .Times(3)
       .WillOnce(Return(validity))
       .WillOnce(Return(validity))
       .WillOnce(Return(invalid));
 
   EXPECT_FALSE([container_ validate]);
 }