Added a force charset override support, bug 43101, r=mscott.

mailnews/mime/src/nsStreamConverter.cpp

@@ -132,6 +132,25 @@ bridge_new_new_uri(void *bridgeStream, nsIURI *aURI)
         charset = uniCharset;
         if (NS_SUCCEEDED(rv) && !charset.IsEmpty())
           msd->options->override_charset = charset.ToNewCString();
+
+        // if the pref says always override and no manual override then set the folder charset to override
+        // in future, the override flag to be per folder instead of a global pref
+        if (charset.IsEmpty()) {
+          nsresult rv;
+          nsCOMPtr <nsIPref> prefs = do_GetService(kPrefCID, &rv);
+          if (NS_SUCCEEDED(rv) && prefs) 
+          {
+            PRBool  force_override;
+            rv = prefs->GetBoolPref("mailnews.force_charset_override", &force_override);
+            if (NS_SUCCEEDED(rv) && force_override) 
+            {
+              i18nUrl->GetFolderCharset(getter_Copies(uniCharset));
+              nsAutoString charset(uniCharset);
+              if (!charset.IsEmpty())
+                msd->options->override_charset = charset.ToNewCString();
+            }
+          }
+        }
       }
       char *urlString;
       if (NS_SUCCEEDED(aURI->GetSpec(&urlString)))