Update uses of UTF conversions in content/ to use the base:: namespace.

content/browser/accessibility/browser_accessibility_cocoa.mm

 // 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 <execinfo.h>
 
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 
 #include <map>
 
@@ skipping 1281 matching lines @@
         NSAccessibilityDisclosingAttribute,
         NSAccessibilityDisclosedByRowAttribute,
         NSAccessibilityDisclosureLevelAttribute,
         NSAccessibilityDisclosedRowsAttribute,
         nil]];
   } else if ([role isEqualToString:NSAccessibilityRowRole]) {
     if (browserAccessibility_->parent()) {
       base::string16 parentRole;
       browserAccessibility_->parent()->GetHtmlAttribute(
           "role", &parentRole);
-      const base::string16 treegridRole(ASCIIToUTF16("treegrid"));
+      const base::string16 treegridRole(base::ASCIIToUTF16("treegrid"));
       if (parentRole == treegridRole) {
         [ret addObjectsFromArray:[NSArray arrayWithObjects:
             NSAccessibilityDisclosingAttribute,
             NSAccessibilityDisclosedByRowAttribute,
             NSAccessibilityDisclosureLevelAttribute,
             NSAccessibilityDisclosedRowsAttribute,
             nil]];
       } else {
         [ret addObjectsFromArray:[NSArray arrayWithObjects:
             NSAccessibilityIndexAttribute,
@@ skipping 162 matching lines @@
     return [super hash];
   return browserAccessibility_->renderer_id();
 }
 
 - (BOOL)accessibilityShouldUseUniqueId {
   return YES;
 }
 
 @end