Use a direct include of strings headers in content/browser/, part 1.

content/browser/accessibility/accessibility_tree_formatter.h

 // 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.
 
 #ifndef CONTENT_BROWSER_ACCESSIBILITY_ACCESSIBILITY_TREE_FORMATTER_H_
 #define CONTENT_BROWSER_ACCESSIBILITY_ACCESSIBILITY_TREE_FORMATTER_H_
 
 #include <vector>
 
 #include "base/files/file_path.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "content/browser/accessibility/browser_accessibility.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 class RenderViewHost;
 
 // A utility class for formatting platform-specific accessibility information,
@@ skipping 116 matching lines @@
 
   // Filters used when formatting the accessibility tree as text.
   std::vector<Filter> filters_;
 
   DISALLOW_COPY_AND_ASSIGN(AccessibilityTreeFormatter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ACCESSIBILITY_ACCESSIBILITY_TREE_FORMATTER_H_