Improve Mojo permission service and chrome::PermissionManager observing.

chrome/browser/permissions/permission_manager.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/permissions/permission_manager.h"
 
 #include "base/callback.h"
 #include "chrome/browser/content_settings/permission_context_base.h"
 #include "chrome/browser/permissions/permission_context.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 189 matching lines @@
 
   if (subscriptions_.IsEmpty())
     profile_->GetHostContentSettingsMap()->RemoveObserver(this);
 }
 
 void PermissionManager::OnContentSettingChanged(
     const ContentSettingsPattern& primary_pattern,
     const ContentSettingsPattern& secondary_pattern,
     ContentSettingsType content_type,
     std::string resource_identifier) {
+  std::list<base::Closure> callbacks;
+
   for (SubscriptionsMap::iterator iter(&subscriptions_);
        !iter.IsAtEnd(); iter.Advance()) {
     Subscription* subscription = iter.GetCurrentValue();
     if (PermissionTypeToContentSetting(subscription->permission) !=
         content_type) {
       continue;
     }
 
     if (primary_pattern.IsValid() &&
         !primary_pattern.Matches(subscription->requesting_origin))
       continue;
     if (secondary_pattern.IsValid() &&
         !secondary_pattern.Matches(subscription->embedding_origin))
       continue;
 
     ContentSetting new_value =
         PermissionContext::Get(profile_, subscription->permission)
             ->GetPermissionStatus(subscription->requesting_origin,
                                   subscription->embedding_origin);
     if (subscription->current_value == new_value)
       continue;
 
     subscription->current_value = new_value;
-    subscription->callback.Run(ContentSettingToPermissionStatus(new_value));
+
+    // Add the callback to |callbacks| which will be run after the loop to
+    // prevent re-entrance issues.
+    callbacks.push_back(
+        base::Bind(subscription->callback,
+                   ContentSettingToPermissionStatus(new_value)));
   }
+
+  for (const auto& callback : callbacks)
+    callback.Run();
 }