Implement 'Do Not Track' header

chrome/common/pref_names.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.
 
 // Constants for the names of various preferences, for easier changing.
 
 #ifndef CHROME_COMMON_PREF_NAMES_H_
 #define CHROME_COMMON_PREF_NAMES_H_
 
 #include <stddef.h>
@@ skipping 331 matching lines @@
 extern const char kAutofillNegativeUploadRate[];
 extern const char kAutofillPersonalDataManagerFirstRun[];
 extern const char kEditBookmarksEnabled[];
 
 extern const char kEnableTranslate[];
 extern const char kPinnedTabs[];
 
 extern const char kDisable3DAPIs[];
 extern const char kEnableHyperlinkAuditing[];
 extern const char kEnableReferrers[];
+extern const char kEnableDoNotTrack[];
 
 extern const char kImportBookmarks[];
 extern const char kImportHistory[];
 extern const char kImportHomepage[];
 extern const char kImportSearchEngine[];
 extern const char kImportSavedPasswords[];
 
 extern const char kEnterpriseWebStoreURL[];
 extern const char kEnterpriseWebStoreName[];
 
@@ skipping 375 matching lines @@
 #endif
 
 extern const char kInManagedMode[];
 
 extern const char kNetworkProfileWarningsLeft[];
 extern const char kNetworkProfileLastWarningTime[];
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_