cros: Don't send duplicate UserSession mojo messages to ash

chrome/browser/ui/ash/session_controller_client.cc

 // Copyright 2016 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/ui/ash/session_controller_client.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "ash/public/cpp/session_types.h"
@@ skipping 374 matching lines @@
 void SessionControllerClient::SendUserSession(const User& user) {
   ash::mojom::UserSessionPtr user_session = UserToUserSession(user);
 
   // Bail if the user has no session. Currently the only code path that hits
   // this condition is from OnUserImageChanged when user images are changed
   // on the login screen (e.g. policy change that adds a public session user,
   // or tests that create new users on the login screen).
   if (!user_session)
     return;
 
-  // TODO(jamescook): Only send if it changed. This will require an Equals()
-  // method for gfx::ImageSkia to allow mojom::UserSession comparison.
-  // http://crbug.com/714689
-  session_controller_->UpdateUserSession(std::move(user_session));
+  if (user_session != last_sent_user_session_) {
+    last_sent_user_session_ = user_session->Clone();
+    session_controller_->UpdateUserSession(std::move(user_session));
+  }
 }
 
 void SessionControllerClient::SendUserSessionOrder() {
   UserManager* const user_manager = UserManager::Get();
 
   const UserList logged_in_users = user_manager->GetLoggedInUsers();
   std::vector<uint32_t> user_session_ids;
   for (auto* user : user_manager->GetLRULoggedInUsers()) {
     const uint32_t user_session_id = GetSessionId(*user);
     DCHECK_NE(0u, user_session_id);
     user_session_ids.push_back(user_session_id);
   }
 
   session_controller_->SetUserSessionOrder(user_session_ids);
 }