Removing x-x509-user-cert mime handler.

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 a21f7b706596c5133d8b63d46564285e2e8517f6..5a0921546ca2b5e0786912e229471268029d52dc 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -458,12 +458,21 @@ void ChromeDownloadManagerDelegate::OpenDownload(DownloadItem* download) {
         profile_, chrome::GetActiveDesktop()));
     browser = browser_displayer->browser();
   }
+
   content::OpenURLParams params(
       net::FilePathToFileURL(download->GetTargetFilePath()),
       content::Referrer(),
       NEW_FOREGROUND_TAB,
       ui::PAGE_TRANSITION_LINK,
       false);
+
+  if (download->GetTargetFilePath().MatchesExtension(
+          FILE_PATH_LITERAL(".crt"))) {
+    params = content::OpenURLParams(GURL("chrome://settings/certificates"),
+                                    content::Referrer(), NEW_FOREGROUND_TAB,
+                                    ui::PAGE_TRANSITION_LINK, false);
+  }
+
   browser->OpenURL(params);
   RecordDownloadOpenMethod(DOWNLOAD_OPEN_METHOD_DEFAULT_BROWSER);
 #else
@@ -729,6 +738,12 @@ void ChromeDownloadManagerDelegate::OnDownloadTargetDetermined(
 
 bool ChromeDownloadManagerDelegate::IsOpenInBrowserPreferreredForFile(
     const base::FilePath& path) {
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+  if (path.MatchesExtension(FILE_PATH_LITERAL(".crt"))) {
+    return true;
+  }
+#endif
+
 #if defined(OS_WIN) || defined(OS_LINUX) || \
     (defined(OS_MACOSX) && !defined(OS_IOS))
   if (path.MatchesExtension(FILE_PATH_LITERAL(".pdf"))) {