chromeos: make mash use MultiUserWindowManagerChromeOS

Ash's MultiUserWindowManagerBridge now creates ash::MultiUserWindowManager
in multi-process mode.

BUG=875111
TEST=covered by tests

Change-Id: I9702b18b453ae4cdde5aad4a8774e2c510e4e9f1
Reviewed-on: https://chromium-review.googlesource.com/c/1355484
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612472}

ash/session/session_controller.cc

@@ -82,6 +82,11 @@ int SessionController::NumberOfLoggedInUsers() const {
   return static_cast<int>(user_sessions_.size());
 }
 
+AccountId SessionController::GetActiveAccountId() const {
+  return user_sessions_.empty() ? AccountId()
+                                : user_sessions_[0]->user_info->account_id;
+}
+
 AddUserSessionPolicy SessionController::GetAddUserPolicy() const {
   return add_user_session_policy_;
 }

ash/session/session_controller.h

@@ -54,6 +54,10 @@ class ASH_EXPORT SessionController : public mojom::SessionController {
   // no session in progress or no active user.
   int NumberOfLoggedInUsers() const;
 
+  // Returns the active account. If no users are logged in this returns an empty
+  // AccountId.
+  AccountId GetActiveAccountId() const;
+
   // Gets the policy of adding a user session to ash.
   AddUserSessionPolicy GetAddUserPolicy() const;
 

ash/ws/multi_user_window_manager_bridge.cc

@@ -5,8 +5,11 @@
 #include "ash/ws/multi_user_window_manager_bridge.h"
 
 #include "ash/multi_user/multi_user_window_manager.h"
+#include "ash/session/session_controller.h"
+#include "ash/shell.h"
 #include "services/ws/window_tree.h"
 #include "ui/aura/window.h"
+#include "ui/base/ui_base_features.h"
 
 namespace ash {
 
@@ -26,8 +29,19 @@ MultiUserWindowManagerBridge::~MultiUserWindowManagerBridge() {
 
 void MultiUserWindowManagerBridge::SetClient(
     mojom::MultiUserWindowManagerClientAssociatedPtrInfo client_info) {
+  multi_user_window_manager_.reset();
   client_.Bind(std::move(client_info));
-  ash::MultiUserWindowManager::Get()->SetClient(client_.get());
+  if (features::IsMultiProcessMash()) {
+    // NOTE: there is nothing stopping mulitple MultiUserWindowManagerBridges
+    // from being created (because multiple clients ask for
+    // ash::mojom::MultiUserWindowManager). This code is assuming only a single
+    // client is used at a time.
+    multi_user_window_manager_ = std::make_unique<ash::MultiUserWindowManager>(
+        client_.get(), nullptr,
+        Shell::Get()->session_controller()->GetActiveAccountId());
+  } else {
+    ash::MultiUserWindowManager::Get()->SetClient(client_.get());
+  }
 }
 
 void MultiUserWindowManagerBridge::SetWindowOwner(ws::Id window_id,

ash/ws/multi_user_window_manager_bridge.h

@@ -20,7 +20,11 @@ class WindowTree;
 
 namespace ash {
 
-// Trivially forwards calls to MultiUserWindowManager.
+class MultiUserWindowManager;
+
+// Responsible for forwarding calls to MultiUserWindowManager. In multi-process
+// mash mode *this* owns the MultiUserWindowManager. In all other cases chrome
+// owns the MultiUserWindowManager.
 class MultiUserWindowManagerBridge : public mojom::MultiUserWindowManager,
                                      public ws::WindowManagerInterface {
  public:
@@ -41,6 +45,8 @@ class MultiUserWindowManagerBridge : public mojom::MultiUserWindowManager,
   ws::WindowTree* window_tree_;
   mojo::AssociatedBinding<mojom::MultiUserWindowManager> binding_;
   mojom::MultiUserWindowManagerClientAssociatedPtr client_;
+  // Only valid in MultiUserWindowManager.
+  std::unique_ptr<ash::MultiUserWindowManager> multi_user_window_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(MultiUserWindowManagerBridge);
 };

chrome/browser/ui/ash/multi_user/multi_user_window_manager.cc

@@ -4,14 +4,12 @@
 
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 
-#include "base/logging.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager_stub.h"
 #include "chrome/browser/ui/ash/session_controller_client.h"
 #include "components/account_id/account_id.h"
 #include "components/user_manager/user_info.h"
 #include "components/user_manager/user_manager.h"
-#include "ui/base/ui_base_features.h"
 
 namespace {
 MultiUserWindowManager* g_multi_user_window_manager_instance = nullptr;
@@ -24,10 +22,7 @@ MultiUserWindowManager* MultiUserWindowManager::GetInstance() {
 
 MultiUserWindowManager* MultiUserWindowManager::CreateInstance() {
   DCHECK(!g_multi_user_window_manager_instance);
-  // TODO(crbug.com/875111): Enable this component in Mash. The object owns a
-  // UserSwitchAnimatorChromeOS with direct ash dependencies.
-  if (!features::IsMultiProcessMash() &&
-      SessionControllerClient::IsMultiProfileAvailable()) {
+  if (SessionControllerClient::IsMultiProfileAvailable()) {
     MultiUserWindowManagerChromeOS* manager =
         new MultiUserWindowManagerChromeOS(
             user_manager::UserManager::Get()->GetActiveUser()->GetAccountId());

chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.h

@@ -163,10 +163,8 @@ class MultiUserWindowManagerChromeOS
   // The notification registrar to track the creation of browser windows.
   content::NotificationRegistrar registrar_;
 
-  // TODO: this won't work in the multi-process mash case. What needs to happen
-  // for the multi-process case is MultiUserWindowManagerDelegate needs to be
-  // converted to a mojom that ash uses to call this code.
-  // https://crbug.com/875111.
+  // This is *only* created in classic and single-process mash cases. In
+  // multi-process mash Ash creates the MultiUserWindowManager.
   std::unique_ptr<ash::MultiUserWindowManager> ash_multi_user_window_manager_;
 
   // Only used for windows created for the window-service. For example,