Add option to open PDFs in system viewer to OS X and Linux.

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 468 matching lines @@
 
 extern const char kBrowserWindowPlacement[];
 extern const char kBrowserWindowPlacementPopup[];
 extern const char kTaskManagerWindowPlacement[];
 extern const char kAppWindowPlacement[];
 extern const char kMemoryCacheSize[];
 
 extern const char kDownloadDefaultDirectory[];
 extern const char kDownloadExtensionsToOpen[];
 extern const char kDownloadDirUpgraded[];
-#if defined(OS_WIN)
-extern const char kOpenPdfDownloadInAdobeReader[];
+#if defined(OS_WIN) || defined(OS_LINUX) || \
+    (defined(OS_MACOSX) && !defined(OS_IOS))
+extern const char kOpenPdfDownloadInSystemReader[];
 #endif
 
 extern const char kSaveFileDefaultDirectory[];
 extern const char kSaveFileType[];
 
 extern const char kAllowFileSelectionDialogs[];
 extern const char kDefaultTasksByMimeType[];
 extern const char kDefaultTasksBySuffix[];
 
 extern const char kSelectFileLastDirectory[];
@@ skipping 299 matching lines @@
 
 extern const char kQuickCheckEnabled[];
 extern const char kBrowserGuestModeEnabled[];
 extern const char kBrowserAddPersonEnabled[];
 
 extern const char kEasyUnlockHardlockState[];
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_