WIP CallbackList in action

chrome/browser/user_style_sheet_watcher.cc

Index: chrome/browser/user_style_sheet_watcher.cc
diff --git a/chrome/browser/user_style_sheet_watcher.cc b/chrome/browser/user_style_sheet_watcher.cc
index a8774b5f01ac06c167eba1724a96eb5981f43fb1..be713197fb6fac67317af382183ef0a87845af59 100644
--- a/chrome/browser/user_style_sheet_watcher.cc
+++ b/chrome/browser/user_style_sheet_watcher.cc
@@ -6,6 +6,7 @@
 
 #include "base/base64.h"
 #include "base/bind.h"
+#include "base/callback_list.h"
 #include "base/file_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/notification_service.h"
@@ -57,7 +58,8 @@ class UserStyleSheetLoader
   void LoadStyleSheet(const base::FilePath& style_sheet_file);
 
   // Register a callback to be called whenever the stylesheet gets updated.
-  void RegisterOnStyleSheetUpdatedCallback(const base::Closure& callback);
+  base::Closure RegisterOnStyleSheetUpdatedCallback(
+      const base::Closure& callback);
 
   // Send out a notification if the stylesheet has already been loaded.
   void NotifyLoaded();
@@ -78,7 +80,7 @@ class UserStyleSheetLoader
   // Whether the stylesheet has been loaded.
   bool has_loaded_;
 
-  std::vector<base::Closure> on_loaded_callbacks_;
+  CallbackList<base::Closure> on_loaded_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(UserStyleSheetLoader);
 };
@@ -87,18 +89,14 @@ UserStyleSheetLoader::UserStyleSheetLoader()
     : has_loaded_(false) {
 }
 
-void UserStyleSheetLoader::RegisterOnStyleSheetUpdatedCallback(
+base::Closure UserStyleSheetLoader::RegisterOnStyleSheetUpdatedCallback(
     const base::Closure& callback) {
-  on_loaded_callbacks_.push_back(callback);
+  return on_loaded_callbacks_.RegisterCallback(callback);
 }
 
 void UserStyleSheetLoader::NotifyLoaded() {
-  if (has_loaded_) {
-    for (size_t i = 0; i < on_loaded_callbacks_.size(); ++i) {
-      if (!on_loaded_callbacks_[i].is_null())
-        on_loaded_callbacks_[i].Run();
-    }
-  }
+  if (has_loaded_)
+    FOR_EACH_CALLBACK(base::Closure, on_loaded_callbacks_);
 }
 
 void UserStyleSheetLoader::NotifyPathChanged(const base::FilePath& path,
@@ -139,7 +137,7 @@ void UserStyleSheetLoader::LoadStyleSheet(
 }
 
 UserStyleSheetLoader::~UserStyleSheetLoader() {
-  on_loaded_callbacks_.clear();
+  on_loaded_callbacks_.Clear();
 }
 
 void UserStyleSheetLoader::SetStyleSheet(const GURL& url) {
@@ -194,9 +192,9 @@ GURL UserStyleSheetWatcher::user_style_sheet() const {
   return loader_->user_style_sheet();
 }
 
-void UserStyleSheetWatcher::RegisterOnStyleSheetUpdatedCallback(
+base::Closure UserStyleSheetWatcher::RegisterOnStyleSheetUpdatedCallback(
     const base::Closure& callback) {
-  loader_->RegisterOnStyleSheetUpdatedCallback(callback);
+  return loader_->RegisterOnStyleSheetUpdatedCallback(callback);
 }
 
 void UserStyleSheetWatcher::Observe(int type,