[multiball] Create SceneState and Controller in AppDelegate.

On iOS 12, and on iOS 13 with no multiwindow plist keys, iOS doesn't
create a SceneDelegate, which would normally take care of creating a
SceneState and a SceneController. Do this in AppDelegate.

Bug: none
Change-Id: Iaa3f505bbe588f75a9fe1c3728c773ba82e32162
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789536
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Auto-Submit: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700167}

ios/chrome/app/BUILD.gn

@@ -239,6 +239,7 @@ source_set("app_internal") {
     "//ios/chrome/browser/ui/toolbar:toolbar_ui",
     "//ios/chrome/browser/ui/toolbar/public",
     "//ios/chrome/browser/ui/util",
+    "//ios/chrome/browser/ui/util:multiwindow_util",
     "//ios/chrome/browser/ui/webui:webui_internal",
     "//ios/chrome/browser/upgrade",
     "//ios/chrome/browser/url_loading",

ios/chrome/app/main_application_delegate.mm

@@ -4,6 +4,7 @@
 
 #import "ios/chrome/app/main_application_delegate.h"
 
+#include "base/ios/ios_util.h"
 #include "base/mac/foundation_util.h"
 #import "ios/chrome/app/application_delegate/app_navigation.h"
 #import "ios/chrome/app/application_delegate/app_state.h"
@@ -18,6 +19,9 @@
 #import "ios/chrome/app/chrome_overlay_window.h"
 #import "ios/chrome/app/main_application_delegate_testing.h"
 #import "ios/chrome/app/main_controller.h"
+#import "ios/chrome/browser/ui/main/scene_controller.h"
+#import "ios/chrome/browser/ui/main/scene_state.h"
+#include "ios/chrome/browser/ui/util/multi_window_support.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #include "ios/public/provider/chrome/browser/signin/chrome_identity_service.h"
 #import "ios/testing/perf/startupLoggers.h"
@@ -47,6 +51,14 @@
   id<TabSwitching> _tabSwitcherProtocol;
 }
 
+// The state representing the only "scene" on iOS 12. On iOS 13, only created
+// temporarily before multiwindow is fully implemented to also represent the
+// only scene.
+@property(nonatomic, strong) SceneState* sceneState;
+
+// The controller for |sceneState|.
+@property(nonatomic, strong) SceneController* sceneController;
+
 @end
 
 @implementation MainApplicationDelegate
@@ -66,6 +78,15 @@
     _tabSwitcherProtocol = _mainController;
     _appNavigation = _mainController;
     [_mainController setAppState:_appState];
+
+    if (!IsMultiwindowSupported()) {
+      // When multiwindow is not supported, this object holds a "scene" state
+      // and a "scene" controller. This allows the rest of the app to be mostly
+      // multiwindow-agnostic.
+      _sceneState = [[SceneState alloc] init];
+      _sceneController =
+          [[SceneController alloc] initWithSceneState:_sceneState];
+    }
   }
   return self;
 }

ios/chrome/browser/ui/util/BUILD.gn

@@ -2,6 +2,29 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
+import("//ios/build/chrome_build.gni")
+
+buildflag_header("ios_multi_window_buildflags") {
+  header = "multi_window_buildflags.h"
+  header_dir = "ios/chrome/browser/ui/util"
+  flags = [ "IOS_MULTIWINDOW_ENABLED=$ios_enable_multi_window" ]
+}
+
+source_set("multiwindow_util") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+
+  sources = [
+    "multi_window_support.h",
+    "multi_window_support.mm",
+  ]
+
+  deps = [
+    ":ios_multi_window_buildflags",
+    "//base",
+  ]
+}
+
 source_set("util") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [

ios/chrome/browser/ui/util/multi_window_support.h

+// Copyright 2019 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.
+
+#ifndef IOS_CHROME_BROWSER_UI_UTIL_MULTI_WINDOW_SUPPORT_H_
+#define IOS_CHROME_BROWSER_UI_UTIL_MULTI_WINDOW_SUPPORT_H_
+
+// Returns true if multiwindow is supported on this OS version and is enabled in
+// the current build configuration. Does not check if this device can actually
+// show multiple windows (e.g. on iPhone): use [UIApplication
+// supportsMultipleScenes] instead.
+bool IsMultiwindowSupported();
+
+#endif  // IOS_CHROME_BROWSER_UI_UTIL_MULTI_WINDOW_SUPPORT_H_

ios/chrome/browser/ui/util/multi_window_support.mm

+// Copyright 2019 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.
+
+#import "ios/chrome/browser/ui/util/multi_window_support.h"
+
+#include "base/ios/ios_util.h"
+#include "ios/chrome/browser/ui/util/multi_window_buildflags.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+bool IsMultiwindowSupported() {
+  return BUILDFLAG(IOS_MULTIWINDOW_ENABLED) &&
+         base::ios::IsRunningOnIOS13OrLater();
+}