Adds a pref and a policy to decide if PDFs should always be opened externally.

chrome/browser/ui/webui/options/content_settings_handler.cc

Index: chrome/browser/ui/webui/options/content_settings_handler.cc
diff --git a/chrome/browser/ui/webui/options/content_settings_handler.cc b/chrome/browser/ui/webui/options/content_settings_handler.cc
index 776e9337f92cdc8e56cccef28c9536ce9d0e4123..9d1a57614d89515622f4eddc5bf71a36540856e0 100644
--- a/chrome/browser/ui/webui/options/content_settings_handler.cc
+++ b/chrome/browser/ui/webui/options/content_settings_handler.cc
@@ -505,6 +505,10 @@ void ContentSettingsHandler::GetLocalizedValues(
     {"keygenHeader", IDS_KEYGEN_HEADER},
     {"keygenAllow", IDS_KEYGEN_ALLOW_RADIO},
     {"keygenBlock", IDS_KEYGEN_DONOTALLOW_RADIO},
+    // PDF Plugin filter.
+    {"pdfTabLabel", IDS_PDF_TAB_LABEL},
+    {"pdfHeader", IDS_PDF_HEADER},
+    {"pdfEnable", IDS_PDF_ENABLE_CHECKBOX},
   };
 
   RegisterStrings(localized_strings, resources, arraysize(resources));