Expand Chrome OS ARC support to create one tree source per package

chrome/browser/extensions/api/automation_internal/automation_event_router.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/automation_internal/automation_event_router.h"
 
 #include <algorithm>
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 92 matching lines @@
         content::RenderProcessHost::FromID(listener.process_id);
     rph->Send(new ExtensionMsg_AccessibilityLocationChange(
         listener.routing_id,
         params));
   }
 }
 
 void AutomationEventRouter::DispatchTreeDestroyedEvent(
     int tree_id,
     content::BrowserContext* browser_context) {
+  if (listeners_.empty())
+    return;
+
   browser_context = browser_context ? browser_context : active_profile_;
   std::unique_ptr<base::ListValue> args(
       api::automation_internal::OnAccessibilityTreeDestroyed::Create(tree_id));
   std::unique_ptr<Event> event(new Event(
       events::AUTOMATION_INTERNAL_ON_ACCESSIBILITY_TREE_DESTROYED,
       api::automation_internal::OnAccessibilityTreeDestroyed::kEventName,
       std::move(args)));
   event->restrict_to_browser_context = browser_context;
   EventRouter::Get(browser_context)->BroadcastEvent(std::move(event));
 }
@@ skipping 84 matching lines @@
     // only mark one as active.
     listener.is_active_profile = (extension_id_count == 1 ||
                                   rph->GetBrowserContext() == active_profile_);
 #else
     listener.is_active_profile = true;
 #endif
   }
 }
 
 }  // namespace extensions