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

chrome/browser/download/download_prefs.h

Index: chrome/browser/download/download_prefs.h
diff --git a/chrome/browser/download/download_prefs.h b/chrome/browser/download/download_prefs.h
index 8d3db57d3e675b58c2ea8e401f148cc04d7dcb83..e4d82594aa3b474cd1c8bfd2c5a6b5756221b7be 100644
--- a/chrome/browser/download/download_prefs.h
+++ b/chrome/browser/download/download_prefs.h
@@ -73,13 +73,15 @@ class DownloadPrefs {
   // Disables auto-open based on file extension.
   void DisableAutoOpenBasedOnExtension(const base::FilePath& file_name);
 
-#if defined(OS_WIN)
+#if defined(OS_WIN) || defined(OS_LINUX) || \
+    (defined(OS_MACOSX) && !defined(OS_IOS))
   // Store the user preference to disk. If |should_open| is true, also disable
   // the built-in PDF plugin. If |should_open| is false, enable the PDF plugin.
-  void SetShouldOpenPdfInAdobeReader(bool should_open);
+  void SetShouldOpenPdfInSystemReader(bool should_open);
 
-  // Return whether the user prefers to open PDF downloads in Adobe Reader.
-  bool ShouldOpenPdfInAdobeReader() const;
+  // Return whether the user prefers to open PDF downloads in the platform's
+  // default reader.
+  bool ShouldOpenPdfInSystemReader() const;
 #endif
 
   void ResetAutoOpen();
@@ -103,8 +105,9 @@ class DownloadPrefs {
                    AutoOpenCompareFunctor> AutoOpenSet;
   AutoOpenSet auto_open_;
 
-#if defined(OS_WIN)
-  bool should_open_pdf_in_adobe_reader_;
+#if defined(OS_WIN) || defined(OS_LINUX) || \
+    (defined(OS_MACOSX) && !defined(OS_IOS))
+  bool should_open_pdf_in_system_reader_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadPrefs);