Fix sessions loss on cold start on iPhones when multiwindow is enabled

Update previousSessionInfo to retain the session id in the case of single
window app, then use it on later runs for the first restore of the run.

Bug: 1131031
Change-Id: I3b245826e9a9c40cb6df1d2e9c4123276c8d73f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2442231
Commit-Queue: Mark Cogan <marq@chromium.org>
Auto-Submit: Mohammad Refaat <mrefaat@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812730}

ios/chrome/app/application_delegate/app_state.h

@@ -90,6 +90,10 @@ initWithBrowserLauncher:(id<BrowserLauncher>)browserLauncher
 // The last window which received a tap.
 @property(nonatomic, weak) UIWindow* lastTappedWindow;
 
+// The SceneSession ID for the last session, where the Device doesn't support
+// multiple windows.
+@property(nonatomic, strong) NSString* previousSingleWindowSessionID;
+
 // Saves the launchOptions to be used from -newTabFromLaunchOptions. If the
 // application is in background, initialize the browser to basic. If not, launch
 // the browser.

ios/chrome/app/main_controller.mm

@@ -480,6 +480,12 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
           moveAsideSessionInformationForBrowserState:chromeBrowserState];
     }
   }
+  if (!IsMultipleScenesSupported() && IsMultiwindowSupported()) {
+    NSSet<NSString*>* previousSessions =
+        [PreviousSessionInfo sharedInstance].connectedSceneSessionsIDs;
+    DCHECK(previousSessions.count <= 1);
+    self.appState.previousSingleWindowSessionID = [previousSessions anyObject];
+  }
   [[PreviousSessionInfo sharedInstance] resetConnectedSceneSessionIDs];
 
   // Initialize and set the main browser state.

ios/chrome/browser/sessions/session_restoration_browser_agent.mm

@@ -71,9 +71,6 @@ SessionRestorationBrowserAgent::~SessionRestorationBrowserAgent() {
 
 void SessionRestorationBrowserAgent::SetSessionID(
     const std::string& session_identifier) {
-  // It's probably incorrect to set this more than once.
-  DCHECK(session_identifier_.empty() ||
-         session_identifier_ == session_identifier);
   session_identifier_ = session_identifier;
 }
 

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

@@ -145,6 +145,7 @@ source_set("main") {
     "//base",
     "//components/translate/core/browser",
     "//ios/chrome/app:mode",
+    "//ios/chrome/app/application_delegate:app_state_header",
     "//ios/chrome/app/resources:launchscreen_xib",
     "//ios/chrome/browser",
     "//ios/chrome/browser/app_launcher",

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

@@ -7,6 +7,7 @@
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/strings/sys_string_conversions.h"
+#import "ios/chrome/app/application_delegate/app_state.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/crash_report/crash_report_helper.h"
@@ -167,10 +168,19 @@
   std::string sessionID = base::SysNSStringToUTF8(self.sessionID);
   SnapshotBrowserAgent::FromBrowser(_mainBrowser.get())
       ->SetSessionID(sessionID);
-  SessionRestorationBrowserAgent::FromBrowser(_mainBrowser.get())
-      ->SetSessionID(sessionID);
-  SessionRestorationBrowserAgent::FromBrowser(_mainBrowser.get())
-      ->RestoreSession();
+
+  // If the OS doesn't support multiple scenes, use the previous run scene ID
+  // for the session restoration.
+  NSString* restoreSessionID = self.sessionID;
+  if (_sceneState.appState.previousSingleWindowSessionID) {
+    restoreSessionID = _sceneState.appState.previousSingleWindowSessionID;
+  }
+  SessionRestorationBrowserAgent* restorationAgent =
+      SessionRestorationBrowserAgent::FromBrowser(_mainBrowser.get());
+  restorationAgent->SetSessionID(base::SysNSStringToUTF8(restoreSessionID));
+  restorationAgent->RestoreSession();
+  restorationAgent->SetSessionID(sessionID);
+
   breakpad::MonitorTabStateForWebStateList(_mainBrowser->GetWebStateList());
   // Follow loaded URLs in the main tab model to send those in case of
   // crashes.

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

@@ -363,8 +363,13 @@ const char kMultiWindowOpenInNewWindowHistogram[] =
   if (self.hasInitializedUI && level == SceneActivationLevelUnattached) {
     if (IsMultiwindowSupported()) {
       if (@available(iOS 13, *)) {
-        [[PreviousSessionInfo sharedInstance]
-            removeSceneSessionID:sceneState.scene.session.persistentIdentifier];
+        if (IsMultipleScenesSupported()) {
+          // If Multiple scenes are not supported, the session shouldn't be
+          // removed as it can be used for normal restoration.
+          [[PreviousSessionInfo sharedInstance]
+              removeSceneSessionID:sceneState.scene.session
+                                       .persistentIdentifier];
+        }
       }
     }
     [self teardownUI];