Extend chromium_tests trigger to work across masters.

scripts/slave/recipe_modules/chromium_tests/api.py

Index: scripts/slave/recipe_modules/chromium_tests/api.py
diff --git a/scripts/slave/recipe_modules/chromium_tests/api.py b/scripts/slave/recipe_modules/chromium_tests/api.py
index 6faa675252b4fe6740e57878515f6e8e6d61849c..9a0057047653c2a3cbd5ca36a9e470dfdb9b14c9 100644
--- a/scripts/slave/recipe_modules/chromium_tests/api.py
+++ b/scripts/slave/recipe_modules/chromium_tests/api.py
@@ -430,17 +430,22 @@ class ChromiumTestsApi(recipe_api.RecipeApi):
                 self.m.chromium.c.HOST_PLATFORM == 'mac'),
         )
 
-      for loop_buildername, builder_dict in sorted(
+      trigger_specs = []
+      for loop_mastername, loop_buildername, builder_dict in sorted(
           bot_db.bot_configs_matching_parent_buildername(
               mastername, buildername)):
         trigger_spec = {
             'builder_name': loop_buildername,
             'properties': {},
         }
+        if mastername != loop_mastername:
+          trigger_spec['bucket'] = 'master.' + loop_mastername
         for name, value in update_step.presentation.properties.iteritems():
           if name.startswith('got_'):
             trigger_spec['properties']['parent_' + name] = value
-        self.m.trigger(trigger_spec)
+        trigger_specs.append(trigger_spec)
+      if trigger_specs:
+        self.m.trigger(*trigger_specs)
 
     if bot_config.get('archive_build') and not self.m.tryserver.is_tryserver:
       self.m.chromium.archive_build(