[multiball] Enable basic multiwindow operation with flag on.

Adds a startup sequence for when the flag is enabled.
Many features are disabled, but it allows booting up and even
opening a second window.

Details:
* uses scene notifications to connect main+scene controllers
* uses scene notifications for app delegate level plumbing
* fixes window creation w/ flag set

Change-Id: I3f85f430ca916e9a866477582e646ca5b92ce4df
Bug: 1045547
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2097990
Commit-Queue: Mark Cogan <marq@chromium.org>
Auto-Submit: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750638}

ios/chrome/app/main_application_delegate.mm

@@ -20,6 +20,7 @@
 #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_delegate.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"
@@ -129,6 +130,21 @@
     self.sceneState.activationLevel = SceneActivationLevelForegroundInactive;
   }
 
+  if (@available(iOS 13, *)) {
+    if (IsMultiwindowSupported()) {
+      [[NSNotificationCenter defaultCenter]
+          addObserver:self
+             selector:@selector(sceneWillConnect:)
+                 name:UISceneWillConnectNotification
+               object:nil];
+      [[NSNotificationCenter defaultCenter]
+          addObserver:self
+             selector:@selector(sceneDidEnterBackground:)
+                 name:UISceneDidEnterBackgroundNotification
+               object:nil];
+    }
+  }
+
   return requiresHandling;
 }
 
@@ -199,6 +215,59 @@
   [_memoryHelper handleMemoryPressure];
 }
 
+#pragma mark - Scenes lifecycle
+
+- (NSInteger)foregroundSceneCount {
+  DCHECK(IsMultiwindowSupported());
+  if (@available(iOS 13, *)) {
+    NSInteger foregroundSceneCount = 0;
+    for (UIScene* scene in UIApplication.sharedApplication.connectedScenes) {
+      if ((scene.activationState == UISceneActivationStateForegroundInactive) ||
+          (scene.activationState == UISceneActivationStateForegroundActive)) {
+        foregroundSceneCount++;
+      }
+    }
+    return foregroundSceneCount;
+  }
+  return 0;
+}
+
+- (void)sceneWillConnect:(NSNotification*)notification {
+  DCHECK(IsMultiwindowSupported());
+  if (@available(iOS 13, *)) {
+    UIWindowScene* scene = (UIWindowScene*)notification.object;
+    SceneDelegate* sceneDelegate = (SceneDelegate*)scene.delegate;
+    SceneController* sceneController = sceneDelegate.sceneController;
+
+    _tabSwitcherProtocol = sceneController;
+    _tabOpener = sceneController;
+    _appNavigation = sceneController;
+
+    // TODO(crbug.com/1060645): This should be called later, or this flow should
+    // be changed completely.
+    if (self.foregroundSceneCount == 0) {
+      [_appState applicationWillEnterForeground:UIApplication.sharedApplication
+                                metricsMediator:_metricsMediator
+                                   memoryHelper:_memoryHelper
+                                      tabOpener:_tabOpener
+                                  appNavigation:_appNavigation];
+    }
+  }
+}
+
+- (void)sceneDidEnterBackground:(NSNotification*)notification {
+  DCHECK(IsMultiwindowSupported());
+  if (@available(iOS 13, *)) {
+    // When the first scene enters foreground, update the app state.
+    if (self.foregroundSceneCount == 0) {
+      [_appState applicationDidEnterBackground:UIApplication.sharedApplication
+                                  memoryHelper:_memoryHelper
+                       incognitoContentVisible:self.sceneController
+                                                   .incognitoContentVisible];
+    }
+  }
+}
+
 #pragma mark Downloading Data in the Background
 
 - (void)application:(UIApplication*)application

ios/chrome/app/main_controller.mm

@@ -124,8 +124,10 @@
 #include "ios/chrome/browser/ui/history/history_coordinator.h"
 #import "ios/chrome/browser/ui/main/browser_view_wrangler.h"
 #import "ios/chrome/browser/ui/main/scene_controller_guts.h"
+#import "ios/chrome/browser/ui/main/scene_delegate.h"
 #import "ios/chrome/browser/ui/settings/settings_navigation_controller.h"
 #import "ios/chrome/browser/ui/ui_feature_flags.h"
+#include "ios/chrome/browser/ui/util/multi_window_support.h"
 #include "ios/chrome/browser/ui/util/ui_util.h"
 #import "ios/chrome/browser/ui/util/uikit_ui_util.h"
 #import "ios/chrome/browser/ui/webui/chrome_web_ui_ios_controller_factory.h"
@@ -442,6 +444,22 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
 
   // Register all providers before calling any Chromium code.
   [ProviderRegistration registerProviders];
+
+  if (@available(iOS 13, *)) {
+    if (IsMultiwindowSupported()) {
+      // Subscribe for scene connection and disconnection notifications.
+      [[NSNotificationCenter defaultCenter]
+          addObserver:self
+             selector:@selector(sceneWillConnect:)
+                 name:UISceneWillConnectNotification
+               object:nil];
+      [[NSNotificationCenter defaultCenter]
+          addObserver:self
+             selector:@selector(sceneDidActivate:)
+                 name:UISceneDidActivateNotification
+               object:nil];
+    }
+  }
 }
 
 - (void)startUpBrowserBackgroundInitialization {
@@ -602,6 +620,15 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
   BOOL needRestore =
       [self startUpBeforeFirstWindowCreatedAndPrepareForRestorationPostCrash:
                 postCrashLaunch];
+
+  if (@available(iOS 13, *)) {
+    if (IsMultiwindowSupported()) {
+      // The rest of the startup sequence is handled by the Scenes and in
+      // response to notifications.
+      return;
+    }
+  }
+
   [self.sceneController startUpChromeUIPostCrash:postCrashLaunch
                                  needRestoration:needRestore];
   [self startUpAfterFirstWindowCreated];
@@ -648,6 +675,30 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
       triggerSystemPromptForNewUser:YES];
 }
 
+#pragma mark - Scene notifications
+
+// Handler for UISceneWillConnectNotification.
+- (void)sceneWillConnect:(NSNotification*)notification {
+  DCHECK(IsMultiwindowSupported());
+  if (@available(iOS 13, *)) {
+    UIWindowScene* scene =
+        base::mac::ObjCCastStrict<UIWindowScene>(notification.object);
+    SceneDelegate* sceneDelegate =
+        base::mac::ObjCCastStrict<SceneDelegate>(scene.delegate);
+    self.sceneController = sceneDelegate.sceneController;
+    sceneDelegate.sceneController.mainController = self;
+  }
+}
+
+// Handler for UISceneDidActivateNotification.
+- (void)sceneDidActivate:(NSNotification*)notification {
+  DCHECK(IsMultiwindowSupported());
+  if (@available(iOS 13, *)) {
+    if (UIApplication.sharedApplication.connectedScenes.count == 1) {
+      [self startUpAfterFirstWindowCreated];
+    }
+  }
+}
 
 #pragma mark - Property implementation.
 

ios/chrome/browser/crash_report/BUILD.gn

@@ -60,6 +60,7 @@ source_set("crash_report_internal") {
     "//ios/chrome/browser/sessions:serialisation",
     "//ios/chrome/browser/sessions:session_service",
     "//ios/chrome/browser/ui/infobars:feature_flags",
+    "//ios/chrome/browser/ui/util:multiwindow_util",
     "//ios/chrome/browser/web:tab_id_tab_helper",
     "//ios/chrome/browser/web_state_list",
     "//ios/web",

ios/chrome/browser/crash_report/crash_report_helper.mm

@@ -20,6 +20,7 @@
 #include "ios/chrome/browser/crash_report/breakpad_helper.h"
 #import "ios/chrome/browser/crash_report/crash_report_user_application_state.h"
 #import "ios/chrome/browser/crash_report/crash_reporter_breadcrumb_observer.h"
+#import "ios/chrome/browser/ui/util/multi_window_support.h"
 #import "ios/chrome/browser/web/tab_id_tab_helper.h"
 #import "ios/chrome/browser/web_state_list/all_web_state_observation_forwarder.h"
 #import "ios/chrome/browser/web_state_list/web_state_list.h"
@@ -216,6 +217,11 @@ const NSString* kDocumentMimeType = @"application/pdf";
 }
 
 - (void)observeWebStateList:(WebStateList*)webStateList {
+  if (_allWebStateObservationForwarder && IsMultiwindowSupported()) {
+    // TODO(crbug.com/1060658): enable crash reporting on more than one window.
+    return;
+  }
+
   webStateList->AddObserver(_webStateListObserver.get());
   // CrashReporterURLObserver should only observe one webStateList at a time.
   DCHECK(!_allWebStateObservationForwarder);

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

@@ -154,6 +154,7 @@ source_set("browser_view") {
     "//ios/chrome/browser/ui/toolbar_container:feature_flags",
     "//ios/chrome/browser/ui/translate:legacy_translate",
     "//ios/chrome/browser/ui/util",
+    "//ios/chrome/browser/ui/util:multiwindow_util",
     "//ios/chrome/browser/ui/voice",
     "//ios/chrome/browser/upgrade",
     "//ios/chrome/browser/url_loading",

ios/chrome/browser/ui/browser_view/browser_view_controller.mm

@@ -141,6 +141,7 @@
 #import "ios/chrome/browser/ui/toolbar_container/toolbar_container_features.h"
 #include "ios/chrome/browser/ui/ui_feature_flags.h"
 #import "ios/chrome/browser/ui/util/keyboard_observer_helper.h"
+#import "ios/chrome/browser/ui/util/multi_window_support.h"
 #import "ios/chrome/browser/ui/util/named_guide.h"
 #import "ios/chrome/browser/ui/util/named_guide_util.h"
 #import "ios/chrome/browser/ui/util/page_animation_util.h"
@@ -929,6 +930,12 @@ NSString* const kBrowserViewControllerSnackbarCategory =
   if (_broadcasting == broadcasting)
     return;
   _broadcasting = broadcasting;
+
+  if (IsMultiwindowSupported()) {
+    // TODO(crbug.com/1060653): fix fullscreen.
+    return;
+  }
+
   // TODO(crbug.com/790886): Use the Browser's broadcaster once Browsers are
   // supported.
   FullscreenController* fullscreenController =

ios/chrome/browser/ui/main/scene_controller.mm

@@ -195,15 +195,14 @@ const NSTimeInterval kDisplayPromoDelay = 0.1;
     [_sceneState addObserver:self];
     // The window is necessary very early in the app/scene lifecycle, so it
     // should be created right away.
-    if (!self.sceneState.window) {
-      DCHECK(!IsMultiwindowSupported())
-          << "The window must be created by the scene delegate";
+    // When multiwindow is supported, the window is created by SceneDelegate,
+    // and fetched by SceneState from UIScene's windows.
+    if (!IsMultiwindowSupported() && !self.sceneState.window) {
       self.sceneState.window = [[ChromeOverlayWindow alloc]
           initWithFrame:[[UIScreen mainScreen] bounds]];
-
-      _appURLLoadingService = new AppUrlLoadingService();
-      _appURLLoadingService->SetDelegate(self);
     }
+    _appURLLoadingService = new AppUrlLoadingService();
+    _appURLLoadingService->SetDelegate(self);
   }
   return self;
 }
@@ -260,6 +259,13 @@ const NSTimeInterval kDisplayPromoDelay = 0.1;
     return;
   }
 
+  DCHECK(self.mainController);
+  if (IsMultiwindowSupported()) {
+    // TODO(crbug.com/1012697): This should probably be the only code path for
+    // multiwindow and non-multiwindow cases.
+    [self startUpChromeUIPostCrash:NO needRestoration:NO];
+  }
+
   self.hasInitializedUI = YES;
 }
 
@@ -270,6 +276,8 @@ const NSTimeInterval kDisplayPromoDelay = 0.1;
                  needRestoration:(BOOL)needsRestoration {
   DCHECK(!self.browserViewWrangler);
   DCHECK(self.appURLLoadingService);
+  DCHECK(self.mainController);
+  DCHECK(self.mainController.mainBrowserState);
 
   self.browserViewWrangler = [[BrowserViewWrangler alloc]
              initWithBrowserState:self.mainController.mainBrowserState
@@ -337,7 +345,7 @@ const NSTimeInterval kDisplayPromoDelay = 0.1;
   TabModel* otrTabModel = self.incognitoInterface.tabModel;
 
   // Enables UI initializations to query the keyWindow's size.
-  [self.mainController.window makeKeyAndVisible];
+  [self.sceneState.window makeKeyAndVisible];
 
   // Lazy init of mainCoordinator.
   [self.mainCoordinator start];