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

chrome/browser/download/chrome_download_manager_delegate.cc

Index: chrome/browser/download/chrome_download_manager_delegate.cc
diff --git a/chrome/browser/download/chrome_download_manager_delegate.cc b/chrome/browser/download/chrome_download_manager_delegate.cc
index 437856403dfad37f83e38fa013ccfe406a1a6ba0..2a999482d93f0be4fc27f0351ecd49ff4a0f3e6d 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -719,11 +719,10 @@ void ChromeDownloadManagerDelegate::OnDownloadTargetDetermined(
 
 bool ChromeDownloadManagerDelegate::IsOpenInBrowserPreferreredForFile(
     const base::FilePath& path) {
-  // On Windows, PDFs should open in Acrobat Reader if the user chooses.
-#if defined(OS_WIN)
-  if (path.MatchesExtension(FILE_PATH_LITERAL(".pdf")) &&
-      DownloadTargetDeterminer::IsAdobeReaderUpToDate()) {
-    return !download_prefs_->ShouldOpenPdfInAdobeReader();
+#if defined(OS_WIN) || defined(OS_LINUX) || \
+    (defined(OS_MACOSX) && !defined(OS_IOS))
+  if (path.MatchesExtension(FILE_PATH_LITERAL(".pdf"))) {
+    return !download_prefs_->ShouldOpenPdfInSystemReader();
   }
 #endif