Convert string16 to base::string16 in content.

content/browser/web_contents/web_drag_dest_mac_unittest.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 "base/mac/scoped_nsautorelease_pool.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/browser/renderer_host/test_render_view_host.h"
 #import "content/browser/web_contents/web_drag_dest_mac.h"
@@ skipping 67 matching lines @@
   // We can't put a value on the screen size since everyone will have a
   // different one.
   EXPECT_NE(0, screenPoint.y);
 }
 
 TEST_F(WebDragDestTest, URL) {
   NSPasteboard* pboard = nil;
   NSString* url = nil;
   NSString* title = nil;
   GURL result_url;
-  string16 result_title;
+  base::string16 result_title;
 
   // Put a URL on the pasteboard and check it.
   pboard = [NSPasteboard pasteboardWithUniqueName];
   url = @"http://www.google.com/";
   PutURLOnPasteboard(url, pboard);
   EXPECT_TRUE(ui::PopulateURLAndTitleFromPasteboard(
       &result_url, &result_title, pboard, NO));
   EXPECT_EQ(base::SysNSStringToUTF8(url), result_url.spec());
   [pboard releaseGlobally];
 
@@ skipping 57 matching lines @@
   NSString* textString = @"hi there";
   [pboard setString:htmlString forType:NSHTMLPboardType];
   [pboard setString:textString forType:NSStringPboardType];
   [drag_dest_ populateDropData:&data fromPasteboard:pboard];
   EXPECT_EQ(data.url.spec(), "http://www.google.com/");
   EXPECT_EQ(base::SysNSStringToUTF16(textString), data.text.string());
   EXPECT_EQ(base::SysNSStringToUTF16(htmlString), data.html.string());
 
   [pboard releaseGlobally];
 }