Prefix string16 with base:: in ui/.

ui/base/cocoa/find_pasteboard.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.
 
 #import "ui/base/cocoa/find_pasteboard.h"
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 
 NSString* kFindPasteboardChangedNotification =
@@ skipping 59 matching lines @@
                        owner:nil];
     [findPboard setString:findText_.get() forType:NSStringPboardType];
     [[NSNotificationCenter defaultCenter]
         postNotificationName:kFindPasteboardChangedNotification
                       object:self];
   }
 }
 
 @end
 
-string16 GetFindPboardText() {
+base::string16 GetFindPboardText() {
   return base::SysNSStringToUTF16([[FindPasteboard sharedInstance] findText]);
 }