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

ui/base/accessibility/accessible_text_utils.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 UI_BASE_ACCESSIBILITY_ACCESSIBLE_TEXT_UTILS_H_
 #define UI_BASE_ACCESSIBILITY_ACCESSIBLE_TEXT_UTILS_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/ui_export.h"
 
 namespace ui {
 
 // Boundaries that can be passed to FindAccessibleTextBoundary,
 // representing various visual boundaries in (potentially multi-line)
 // text. This is used by assistive technology in order to, for example,
 // retrieve the nearest word to the cursor, or retrieve all of the
 // text from the current cursor position to the end of the line.
 // These should be self-explanatory; "line" here refers to the visual
@@ skipping 22 matching lines @@
 // using the vector of line break character offsets in |line_breaks|.
 size_t UI_EXPORT FindAccessibleTextBoundary(const string16& text,
                                             const std::vector<int>& line_breaks,
                                             TextBoundaryType boundary,
                                             size_t start_offset,
                                             TextBoundaryDirection direction);
 
 }  // namespace ui
 
 #endif  // UI_BASE_ACCESSIBILITY_ACCESSIBLE_TEXT_UTILS_H_