Refactor TabModel initialisation from a saved session.

ios/chrome/browser/tabs/tab_model.mm

Index: ios/chrome/browser/tabs/tab_model.mm
diff --git a/ios/chrome/browser/tabs/tab_model.mm b/ios/chrome/browser/tabs/tab_model.mm
index 7cd840e0bdb9fe53d10612713e34ab5aa7445420..94ee048b52746036e7527c5353657ed8cb9b0594 100644
--- a/ios/chrome/browser/tabs/tab_model.mm
+++ b/ios/chrome/browser/tabs/tab_model.mm
@@ -157,6 +157,7 @@ void CleanCertificatePolicyCache(
                     openedByDOM:(BOOL)openedByDOM
                         atIndex:(NSUInteger)index
                    inBackground:(BOOL)inBackground;
+
 // Call to switch the selected tab. Broadcasts about the change in selection.
 // It's ok for |newTab| to be nil in case the last tab is going away. In that
 // case, the "tab deselected" notification gets sent, but no corresponding
@@ -165,11 +166,20 @@ void CleanCertificatePolicyCache(
 - (void)changeSelectedTabFrom:(Tab*)oldTab
                            to:(Tab*)newTab
                  persistState:(BOOL)persist;
+
 // Tells the snapshot cache the adjacent tab session ids.
 - (void)updateSnapshotCache:(Tab*)tab;
+
 // Helper method that posts a notification with the given name with |tab|
 // in the userInfo dictionary under the kTabModelTabKey.
 - (void)postNotificationName:(NSString*)notificationName withTab:(Tab*)tab;
+
+// Helper method to restore a saved session and control if the state should
+// be persisted or not. Used to implement the public -restoreSessionWindow:
+// method and restoring session in the initialiser.
+- (BOOL)restoreSessionWindow:(SessionWindowIOS*)window
+                persistState:(BOOL)persistState;
+
 @end
 
 @implementation TabModel
@@ -256,56 +266,35 @@ void CleanCertificatePolicyCache(
     _syncedWindowDelegate.reset(new TabModelSyncedWindowDelegate(self));
 
     _tabs.reset([[NSMutableArray alloc] init]);
-    NSNotificationCenter* defaultCenter = [NSNotificationCenter defaultCenter];
     if (window) {
-      web::WebState::CreateParams params(_browserState);
-      for (CRWNavigationManagerStorage* session in window.sessions) {
-        std::unique_ptr<web::WebState> webState =
-            web::WebState::Create(params, session);
-        DCHECK_EQ(webState->GetBrowserState(), _browserState);
-        // Restore the CertificatePolicyCache.
-        UpdateCertificatePolicyCacheFromWebState(webState.get());
-        // Create a new tab for each entry in the window. Don't send delegate
-        // notifications for each restored tab, only when all done.
-        base::scoped_nsobject<Tab> tab(
-            [[Tab alloc] initWithWebState:std::move(webState) model:self]);
-        [tab webController].usePlaceholderOverlay = YES;
-        [tab fetchFavicon];
-        [_tabs addObject:tab];
-
-        TabParentingGlobalObserver::GetInstance()->OnTabParented(
-            tab.get().webState);
-      }
-      if ([_tabs count]) {
-        DCHECK(window.selectedIndex < [_tabs count]);
-        _currentTab.reset([self tabAtIndex:window.selectedIndex]);
-        DCHECK(_currentTab);
-        if (_tabUsageRecorder)
-          _tabUsageRecorder->InitialRestoredTabs(_currentTab, _tabs);
-        // Perform initializations for affiliated objects which update the
-        // session information related to the current tab.
-        [_currentTab updateLastVisitedTimestamp];
-        [self saveSessionImmediately:NO];
-      }
+      DCHECK([_observers empty]);
+      // Restore the session and reset the session metrics (as the event have
+      // not been generated by the user but by a cold start cycle).
+      [self restoreSessionWindow:window persistState:NO];
+      [self resetSessionMetrics];
     }
 
     _orderController.reset(
         [[TabModelOrderController alloc] initWithTabModel:self]);
+
     // Register for resign active notification.
-    [defaultCenter addObserver:self
-                      selector:@selector(willResignActive:)
-                          name:UIApplicationWillResignActiveNotification
-                        object:nil];
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(willResignActive:)
+               name:UIApplicationWillResignActiveNotification
+             object:nil];
     // Register for background notification.
-    [defaultCenter addObserver:self
-                      selector:@selector(applicationDidEnterBackground:)
-                          name:UIApplicationDidEnterBackgroundNotification
-                        object:nil];
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(applicationDidEnterBackground:)
+               name:UIApplicationDidEnterBackgroundNotification
+             object:nil];
     // Register for foregrounding notification.
-    [defaultCenter addObserver:self
-                      selector:@selector(applicationWillEnterForeground:)
-                          name:UIApplicationWillEnterForegroundNotification
-                        object:nil];
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(applicationWillEnterForeground:)
+               name:UIApplicationWillEnterForegroundNotification
+             object:nil];
 
     // Associate with ios::ChromeBrowserState.
     RegisterTabModelWithChromeBrowserState(_browserState, self);
@@ -319,55 +308,7 @@ void CleanCertificatePolicyCache(
 }
 
 - (BOOL)restoreSessionWindow:(SessionWindowIOS*)window {
-  DCHECK(_browserState);
-  DCHECK(window);
-  NSArray* sessions = window.sessions;
-  if (!sessions.count)
-    return NO;
-  size_t oldCount = [_tabs count];
-  size_t index = oldCount;
-  web::WebState::CreateParams params(_browserState);
-  for (CRWNavigationManagerStorage* session in sessions) {
-    std::unique_ptr<web::WebState> webState =
-        web::WebState::Create(params, session);
-    DCHECK_EQ(webState->GetBrowserState(), _browserState);
-    Tab* tab = [self insertTabWithWebState:std::move(webState) atIndex:index++];
-    tab.webController.usePlaceholderOverlay = YES;
-    // Restore the CertificatePolicyCache. Note that after calling Pass()
-    // |webState| is invalid, so we need to get the webstate from |tab|.
-    UpdateCertificatePolicyCacheFromWebState(tab.webState);
-  }
-  DCHECK([_tabs count] > oldCount);
-  // If any tab was restored, the saved selected tab must be selected.
-  if ([_tabs count] > oldCount) {
-    NSUInteger selectedIndex = window.selectedIndex;
-    if (selectedIndex == NSNotFound)
-      selectedIndex = oldCount;
-    else
-      selectedIndex += oldCount;
-    DCHECK(selectedIndex < [_tabs count]);
-    Tab* newTab = [self tabAtIndex:selectedIndex];
-    DCHECK(newTab);
-    [self changeSelectedTabFrom:_currentTab to:newTab persistState:YES];
-
-    // If there was only one tab and it was the new tab page, clobber it.
-    if (oldCount == 1) {
-      Tab* tab = [_tabs objectAtIndex:0];
-      if (tab.url == GURL(kChromeUINewTabURL)) {
-        [self closeTab:tab];
-        if (_tabUsageRecorder)
-          _tabUsageRecorder->InitialRestoredTabs(_currentTab, _tabs);
-        return YES;
-      }
-    }
-    if (_tabUsageRecorder) {
-      _tabUsageRecorder->InitialRestoredTabs(
-          _currentTab,
-          [_tabs subarrayWithRange:NSMakeRange(oldCount,
-                                               [_tabs count] - oldCount)]);
-    }
-  }
-  return NO;
+  return [self restoreSessionWindow:window persistState:YES];
 }
 
 - (void)saveSessionImmediately:(BOOL)immediately {
@@ -1002,6 +943,61 @@ void CleanCertificatePolicyCache(
                                                     userInfo:userInfo];
 }
 
+- (BOOL)restoreSessionWindow:(SessionWindowIOS*)window
+                persistState:(BOOL)persistState {
+  DCHECK(_browserState);
+  DCHECK(window);
+
+  NSArray* sessions = window.sessions;
+  if (!sessions.count)
+    return NO;
+
+  size_t oldCount = [_tabs count];
+  web::WebState::CreateParams params(_browserState);
+
+  for (CRWNavigationManagerStorage* session in sessions) {
+    std::unique_ptr<web::WebState> webState =
+        web::WebState::Create(params, session);
+    DCHECK_EQ(webState->GetBrowserState(), _browserState);
+    Tab* tab =
+        [self insertTabWithWebState:std::move(webState) atIndex:[_tabs count]];
+    tab.webController.usePlaceholderOverlay = YES;
+
+    // Restore the CertificatePolicyCache (note that webState is invalid after
+    // passing it via move semantic to -insertTabWithWebState:atIndex:).
+    UpdateCertificatePolicyCacheFromWebState(tab.webState);
+  }
+  DCHECK_GT([_tabs count], oldCount);
+
+  // Update the selected tab if there was a selected Tab in the saved session.
+  if (window.selectedIndex != NSNotFound) {
+    NSUInteger selectedIndex = window.selectedIndex + oldCount;
+    DCHECK_LT(selectedIndex, [_tabs count]);
+    DCHECK([self tabAtIndex:selectedIndex]);
+    [self changeSelectedTabFrom:_currentTab
+                             to:[self tabAtIndex:selectedIndex]
+                   persistState:persistState];
+  }
+
+  // If there was only one tab and it was the new tab page, clobber it.
+  BOOL closedNTPTab = NO;
+  if (oldCount == 1) {
+    Tab* tab = [_tabs objectAtIndex:0];
+    if (tab.url == GURL(kChromeUINewTabURL)) {
+      [self closeTab:tab];
+      closedNTPTab = YES;
+      oldCount = 0;
+    }
+  }
+  if (_tabUsageRecorder) {
+    _tabUsageRecorder->InitialRestoredTabs(
+        _currentTab,
+        [_tabs
+            subarrayWithRange:NSMakeRange(oldCount, [_tabs count] - oldCount)]);
+  }
+  return closedNTPTab;
+}
+
 #pragma mark - Notification Handlers
 
 // Called when UIApplicationWillResignActiveNotification is received.