Final batch adding real histogram values for extension events.

chrome/browser/extensions/api/preference/chrome_direct_setting_api.cc

 // Copyright 2013 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/preference/chrome_direct_setting_api.h"
 
 #include "base/bind.h"
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
 #include "base/prefs/pref_change_registrar.h"
@@ skipping 127 matching lines @@
     scoped_ptr<base::DictionaryValue> result(new base::DictionaryValue);
     result->Set(preference_api_constants::kValue, value->DeepCopy());
     base::ListValue args;
     args.Append(result.release());
 
     for (const scoped_refptr<const extensions::Extension>& extension :
          ExtensionRegistry::Get(profile_)->enabled_extensions()) {
       const std::string& extension_id = extension->id();
       if (router->ExtensionHasEventListener(extension_id, event_name)) {
         scoped_ptr<base::ListValue> args_copy(args.DeepCopy());
+        // TODO(kalman): Have a histogram value for each pref type.
+        // This isn't so important for the current use case of these
+        // histograms, which is to track which event types are waking up event
+        // pages, or which are delivered to persistent background pages. Simply
+        // "a setting changed" is enough detail for that. However if we try to
+        // use these histograms for any fine-grained logic (like removing the
+        // string event name altogether), or if we discover this event is
+        // firing a lot and want to understand that better, then this will need
+        // to change.
+        events::HistogramValue histogram_value =
+            events::TYPES_PRIVATE_CHROME_DIRECT_SETTING_ON_CHANGE;
         scoped_ptr<Event> event(
-            new Event(events::UNKNOWN, event_name, args_copy.Pass()));
+            new Event(histogram_value, event_name, args_copy.Pass()));
         router->DispatchEventToExtension(extension_id, event.Pass());
       }
     }
   }
 }
 
 }  // namespace chromedirectsetting
 }  // namespace extensions