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

chrome/browser/ui/cocoa/notifications/message_center_tray_bridge_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/notifications/message_center_tray_bridge.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 29 matching lines @@
 
 TEST_F(MessageCenterTrayBridgeTest, StatusItemOnlyAfterFirstNotification) {
   EXPECT_FALSE(status_item());
 
   message_center::RichNotificationData data;
   data.priority = -1;
   scoped_ptr<message_center::Notification> notification(
       new message_center::Notification(
           message_center::NOTIFICATION_TYPE_SIMPLE,
           "1",
-          ASCIIToUTF16("First notification"),
-          ASCIIToUTF16("This is a simple test."),
+          base::ASCIIToUTF16("First notification"),
+          base::ASCIIToUTF16("This is a simple test."),
           gfx::Image(),
           base::string16(),
           message_center::NotifierId(),
           data,
           NULL));
   center_->AddNotification(notification.Pass());
 
   base::RunLoop().RunUntilIdle();
 
   EXPECT_TRUE(status_item());
   EXPECT_EQ(1u, [status_item() unreadCount]);
 
   center_->RemoveNotification("1", /*by_user=*/true);
 
   base::RunLoop().RunUntilIdle();
 
   EXPECT_TRUE(status_item());
 }