Bug 704320 - content/dom changes for meta referrer support. (r=jst)

This enables referrer policies for:
- EventSource         (content/base/src/EventSource)
- XMLHttpRequest      (content/base/src/nsXMLHttpRequest)
- HTML media elements (content/html/content/src/HTMLMediaElement)
- window.open         (embedding/components/windowwatcher)
- window.location     (dom/base/nsLocation)

dom/html/HTMLMediaElement.cpp

@@ -3719,7 +3719,8 @@ void HTMLMediaElement::SetRequestHeaders(nsIHttpChannel* aChannel)
                              EmptyCString(), false);
 
   // Set the Referer header
-  aChannel->SetReferrer(OwnerDoc()->GetDocumentURI());
+  aChannel->SetReferrerWithPolicy(OwnerDoc()->GetDocumentURI(),
+                                  OwnerDoc()->GetReferrerPolicy());
 }
 
 void HTMLMediaElement::FireTimeUpdate(bool aPeriodic)