Use --extra_patchlevel for WebRTC patches on Chromium trybots.

recipe_modules/bot_update/resources/bot_update.py

Index: recipe_modules/bot_update/resources/bot_update.py
diff --git a/recipe_modules/bot_update/resources/bot_update.py b/recipe_modules/bot_update/resources/bot_update.py
index efee4783b0b8afa6084b70a2ab674950b84f0dfd..906d9099f7be77c9a4b3acff3fe5a1f48ab2a53b 100755
--- a/recipe_modules/bot_update/resources/bot_update.py
+++ b/recipe_modules/bot_update/resources/bot_update.py
@@ -1126,6 +1126,10 @@ def apply_rietveld_issue(issue, patchset, root, server, _rev_map, _revision,
     for item in blacklist:
       cmd.extend(['--blacklist', item])
 
+  # TODO(kjellander): Remove this hack when http://crbug.com/611808 is fixed.
+  if root == 'src/third_party/webrtc':
+    cmd.extend(['--extra_patchlevel=1'])
+
   # Only try once, since subsequent failures hide the real failure.
   try:
     call(*cmd, tries=1)