add onEndMsgDownload notification, part of extensibility hooks r=cavin, sr=sspitzer 161226

mailnews/mime/emitters/src/nsMimeHtmlEmitter.cpp

@@ -422,6 +422,12 @@ nsMimeHtmlDisplayEmitter::EndBody()
 {
   UtilityWriteCRLF("</body>");
   UtilityWriteCRLF("</html>");
+  nsCOMPtr<nsIMsgHeaderSink> headerSink; 
+  nsresult rv = GetHeaderSink(getter_AddRefs(headerSink));
+  nsCOMPtr<nsIMsgMailNewsUrl> mailnewsUrl (do_QueryInterface(mURL, &rv));
+  if (headerSink)
+    headerSink->OnEndMsgDownload(mailnewsUrl);
+
   return NS_OK;
 }
 

mailnews/mime/public/nsIMimeMiscStatus.idl

@@ -42,6 +42,7 @@ interface nsIInputStream;
 interface nsIURI;
 interface nsIStreamListener;
 interface nsIChannel;
+interface nsIMsgMailNewsUrl;
 
 [scriptable, uuid(4644FB25-5255-11d3-82B8-444553540002)] 
 interface nsIMimeMiscStatus : nsISupports{
@@ -66,6 +67,7 @@ interface nsIMsgHeaderSink : nsISupports {
 	void handleAttachment(in string contentType, in string url, in wstring displayName, in string
                           uri, in boolean aNotDownloaded);
     void onEndAllAttachments();
+    void onEndMsgDownload(in nsIMsgMailNewsUrl url);
 
 	attribute nsISupports securityInfo;
 };