Use a direct include of strings headers in chrome/browser/d*/.

chrome/browser/diagnostics/diagnostics_test.h

 // Copyright (c) 2011 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 CHROME_BROWSER_DIAGNOSTICS_DIAGNOSTICS_TEST_H_
 #define CHROME_BROWSER_DIAGNOSTICS_DIAGNOSTICS_TEST_H_
 
 #include "base/compiler_specific.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "chrome/browser/diagnostics/diagnostics_model.h"
 
 namespace base {
 class FilePath;
 }
 
 // Represents a single diagnostic test and encapsulates the common
 // functionality across platforms as well.
 // It also Implements the TestInfo interface providing the storage
 // for the outcome of the test.
@@ skipping 45 matching lines @@
   virtual int GetId() = 0;
   // Derived classes override this method do perform the actual test.
   virtual bool ExecuteImpl(DiagnosticsModel::Observer* observer) = 0;
 
   string16 title_;
   string16 additional_info_;
   DiagnosticsModel::TestResult result_;
 };
 
 #endif  // CHROME_BROWSER_DIAGNOSTICS_DIAGNOSTICS_TEST_H_