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..8418be04f1765cdff090e7fa6126920c23443396 100644
--- a/chrome/browser/download/download_prefs.h
+++ b/chrome/browser/download/download_prefs.h
@@ -80,6 +80,14 @@ class DownloadPrefs {
 
   // Return whether the user prefers to open PDF downloads in Adobe Reader.
   bool ShouldOpenPdfInAdobeReader() const;
+#elif defined(OS_MACOSX) || defined(OS_LINUX)
+  // 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 SetShouldOpenPdfInSystemReader(bool should_open);
+
+  // Return whether the user prefers to open PDF downloads in the platform's
+  // default reader.
+  bool ShouldOpenPdfInSystemReader() const;
 #endif
 
   void ResetAutoOpen();
@@ -105,6 +113,8 @@ class DownloadPrefs {
 
 #if defined(OS_WIN)
   bool should_open_pdf_in_adobe_reader_;
+#elif defined(OS_MACOSX) || defined(OS_LINUX)
+  bool should_open_pdf_in_system_reader_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadPrefs);