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 13 matching lines @@
 #include "chrome/browser/ui/ash/multi_user/user_switch_util.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/grit/theme_resources.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
 #include "components/prefs/pref_service.h"
 #include "components/session_manager/core/session_manager.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/common/service_manager_connection.h"
 #include "content/public/common/service_names.mojom.h"
+#include "mojo/public/cpp/bindings/equals_traits.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/image/image_skia.h"
 
 using session_manager::Session;
 using session_manager::SessionManager;
 using user_manager::UserManager;
 using user_manager::User;
 using user_manager::UserList;
 
 namespace {
 
 SessionControllerClient* g_instance = nullptr;
@@ skipping 48 matching lines @@
 
   return session;
 }
 
 void DoSwitchUser(const AccountId& account_id) {
   UserManager::Get()->SwitchActiveUser(account_id);
 }
 
 }  // namespace
 
+namespace mojo {
+
+// When comparing two mojom::UserSession objects we need to decide if the avatar
+// images are changed. Consider them equal if they have the same storage rather
+// than comparing the backing pixels.
+template <>
+struct EqualsTraits<gfx::ImageSkia, false> {

[yzshen1, 2017/04/25 20:17:22]

Do you need to explicitly put "false" here?
I thought it has got a default value which depends on whether gfx::ImageSkia has
Equals or not.

+  static bool Equals(const gfx::ImageSkia& a, const gfx::ImageSkia& b) {
+    return a.BackedBySameObjectAs(b);
+  }
+};
+
+}  // namespace mojo
+
 SessionControllerClient::SessionControllerClient()
     : binding_(this), weak_ptr_factory_(this) {
   SessionManager::Get()->AddObserver(this);
   UserManager::Get()->AddSessionStateObserver(this);
   UserManager::Get()->AddObserver(this);
 
   registrar_.Add(this, chrome::NOTIFICATION_APP_TERMINATING,
                  content::NotificationService::AllSources());
   registrar_.Add(this, chrome::NOTIFICATION_LOGIN_USER_PROFILE_PREPARED,
                  content::NotificationService::AllSources());
@@ skipping 271 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);
 }