Revert "Fix restoration of session after a crash."

This reverts commit 13de3702.

Reason for revert: breaks '-[ExternalURLSigninTestCase testSignInReauthenticate]' EarlGrey test.

Original change's description:
> Fix restoration of session after a crash.
> 
> Disable sending kTabModelNewTabWillOpenNotification notification
> when the TabModel is restoring a session as this breaks the BVC
> state that does not expect the notification to be sent when a tab
> is added due to session restoration.
> 
> Bug: 763964
> Change-Id: I404487b5a561e43fe4d23303c004e4d3e8701dfe
> Reviewed-on: https://chromium-review.googlesource.com/664557
> Reviewed-by: Rohit Rao (ping after 24h) <rohitrao@chromium.org>
> Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#501614}

TBR=rohitrao@chromium.org,sdefresne@chromium.org

Change-Id: I917e129b14d351bf66527a6620c4f67f97eaa8aa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 763964
Reviewed-on: https://chromium-review.googlesource.com/664706Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501667}

ios/chrome/browser/tabs/BUILD.gn

@@ -58,8 +58,6 @@ source_set("tabs_internal") {
     "tab_model_synced_window_delegate_getter.mm",
     "tab_model_web_state_list_delegate.h",
     "tab_model_web_state_list_delegate.mm",
-    "tab_model_web_usage_enabled_observer.h",
-    "tab_model_web_usage_enabled_observer.mm",
     "tab_parenting_observer.h",
     "tab_parenting_observer.mm",
   ]

ios/chrome/browser/tabs/tab_model.mm

@@ -42,7 +42,6 @@
 #import "ios/chrome/browser/tabs/tab_model_selected_tab_observer.h"
 #import "ios/chrome/browser/tabs/tab_model_synced_window_delegate.h"
 #import "ios/chrome/browser/tabs/tab_model_web_state_list_delegate.h"
-#import "ios/chrome/browser/tabs/tab_model_web_usage_enabled_observer.h"
 #import "ios/chrome/browser/tabs/tab_parenting_observer.h"
 #import "ios/chrome/browser/web/page_placeholder_tab_helper.h"
 #import "ios/chrome/browser/web_state_list/web_state_list.h"
@@ -157,9 +156,6 @@ void CleanCertificatePolicyCache(
   // The delegate for sync.
   std::unique_ptr<TabModelSyncedWindowDelegate> _syncedWindowDelegate;
 
-  // The observer that sends kTabModelNewTabWillOpenNotification notifications.
-  TabModelNotificationObserver* _tabModelNotificationObserver;
-
   // Counters for metrics.
   WebStateListMetricsObserver* _webStateListMetricsObserver;
 
@@ -317,12 +313,7 @@ void CleanCertificatePolicyCache(
     _webStateListObservers.push_back(std::move(webStateListMetricsObserver));
 
     _webStateListObservers.push_back(
-        base::MakeUnique<TabModelWebUsageEnabledObserver>(self));
-
-    auto tabModelNotificationObserver =
-        base::MakeUnique<TabModelNotificationObserver>(self);
-    _tabModelNotificationObserver = tabModelNotificationObserver.get();
-    _webStateListObservers.push_back(std::move(tabModelNotificationObserver));
+        base::MakeUnique<TabModelNotificationObserver>(self));
 
     for (const auto& webStateListObserver : _webStateListObservers)
       _webStateList->AddObserver(webStateListObserver.get());
@@ -578,8 +569,7 @@ void CleanCertificatePolicyCache(
   UnregisterTabModelFromChromeBrowserState(_browserState, self);
   _browserState = nullptr;
 
-  // Clear weak pointer to observers before destroying them.
-  _tabModelNotificationObserver = nullptr;
+  // Clear weak pointer to WebStateListMetricsObserver before destroying it.
   _webStateListMetricsObserver = nullptr;
 
   // Close all tabs. Do this in an @autoreleasepool as WebStateList observers
@@ -656,11 +646,6 @@ void CleanCertificatePolicyCache(
   if (!window.sessions.count)
     return NO;
 
-  // Disable sending the kTabModelNewTabWillOpenNotification notification
-  // while restoring a session as it breaks the BVC (see crbug.com/763964).
-  if (_tabModelNotificationObserver)
-    _tabModelNotificationObserver->set_enabled(false);
-
   int oldCount = _webStateList->count();
   DCHECK_GE(oldCount, 0);
 
@@ -710,10 +695,6 @@ void CleanCertificatePolicyCache(
     _tabUsageRecorder->InitialRestoredTabs(self.currentTab.webState,
                                            restoredWebStates);
   }
-
-  if (_tabModelNotificationObserver)
-    _tabModelNotificationObserver->set_enabled(true);
-
   return closedNTPTab;
 }
 

ios/chrome/browser/tabs/tab_model_notification_observer.h

@@ -15,18 +15,18 @@ class TabModelNotificationObserver : public WebStateListObserver {
   explicit TabModelNotificationObserver(TabModel* tab_model);
   ~TabModelNotificationObserver() override;
 
-  // Controls whether sending notification is enabled or not.
-  void set_enabled(bool enabled) { enabled_ = enabled; }
-
   // WebStateListObserver implementation.
   void WebStateInsertedAt(WebStateList* web_state_list,
                           web::WebState* web_state,
                           int index,
                           bool activating) override;
+  void WebStateReplacedAt(WebStateList* web_state_list,
+                          web::WebState* old_web_state,
+                          web::WebState* new_web_state,
+                          int index) override;
 
  private:
   __weak TabModel* tab_model_;
-  bool enabled_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(TabModelNotificationObserver);
 };

ios/chrome/browser/tabs/tab_model_notification_observer.mm

@@ -12,6 +12,18 @@
 #error "This file requires ARC support."
 #endif
 
+namespace {
+
+// Sets |web_state| web usage enabled property and starts loading the content
+// if necessary.
+void SetWebUsageEnabled(web::WebState* web_state, bool web_usage_enabled) {
+  web_state->SetWebUsageEnabled(web_usage_enabled);
+  if (web_usage_enabled)
+    web_state->GetNavigationManager()->LoadIfNecessary();
+}
+
+}  // namespace
+
 TabModelNotificationObserver::TabModelNotificationObserver(TabModel* tab_model)
     : tab_model_(tab_model) {}
 
@@ -22,8 +34,7 @@ void TabModelNotificationObserver::WebStateInsertedAt(
     web::WebState* web_state,
     int index,
     bool activating) {
-  if (!enabled_)
-    return;
+  SetWebUsageEnabled(web_state, tab_model_.webUsageEnabled);
 
   Tab* tab = LegacyTabHelper::GetTabForWebState(web_state);
   [[NSNotificationCenter defaultCenter]
@@ -35,3 +46,10 @@ void TabModelNotificationObserver::WebStateInsertedAt(
                   }];
 }
 
+void TabModelNotificationObserver::WebStateReplacedAt(
+    WebStateList* web_state_list,
+    web::WebState* old_web_state,
+    web::WebState* new_web_state,
+    int index) {
+  SetWebUsageEnabled(new_web_state, tab_model_.webUsageEnabled);
+}

ios/chrome/browser/tabs/tab_model_web_usage_enabled_observer.h

-// Copyright 2017 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_TABS_TAB_MODEL_WEB_USAGE_ENABLED_OBSERVER_H_
-#define IOS_CHROME_BROWSER_TABS_TAB_MODEL_WEB_USAGE_ENABLED_OBSERVER_H_
-
-#include "base/macros.h"
-#import "ios/chrome/browser/web_state_list/web_state_list_observer.h"
-
-@class TabModel;
-
-class TabModelWebUsageEnabledObserver : public WebStateListObserver {
- public:
-  explicit TabModelWebUsageEnabledObserver(TabModel* tab_model);
-  ~TabModelWebUsageEnabledObserver() override;
-
-  // WebStateListObserver implementation.
-  void WebStateInsertedAt(WebStateList* web_state_list,
-                          web::WebState* web_state,
-                          int index,
-                          bool activating) override;
-  void WebStateReplacedAt(WebStateList* web_state_list,
-                          web::WebState* old_web_state,
-                          web::WebState* new_web_state,
-                          int index) override;
-
- private:
-  __weak TabModel* tab_model_;
-
-  DISALLOW_COPY_AND_ASSIGN(TabModelWebUsageEnabledObserver);
-};
-
-#endif  // IOS_CHROME_BROWSER_TABS_TAB_MODEL_WEB_USAGE_ENABLED_OBSERVER_H_

ios/chrome/browser/tabs/tab_model_web_usage_enabled_observer.mm

-// Copyright 2017 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/tabs/tab_model_web_usage_enabled_observer.h"
-
-#import "ios/chrome/browser/tabs/tab_model.h"
-#import "ios/web/public/web_state/web_state.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-namespace {
-
-// Sets |web_state| web usage enabled property and starts loading the content
-// if necessary.
-void SetWebUsageEnabled(web::WebState* web_state, bool web_usage_enabled) {
-  web_state->SetWebUsageEnabled(web_usage_enabled);
-  if (web_usage_enabled)
-    web_state->GetNavigationManager()->LoadIfNecessary();
-}
-
-}  // namespace
-
-TabModelWebUsageEnabledObserver::TabModelWebUsageEnabledObserver(
-    TabModel* tab_model)
-    : tab_model_(tab_model) {}
-
-TabModelWebUsageEnabledObserver::~TabModelWebUsageEnabledObserver() = default;
-
-void TabModelWebUsageEnabledObserver::WebStateInsertedAt(
-    WebStateList* web_state_list,
-    web::WebState* web_state,
-    int index,
-    bool activating) {
-  SetWebUsageEnabled(web_state, tab_model_.webUsageEnabled);
-}
-
-void TabModelWebUsageEnabledObserver::WebStateReplacedAt(
-    WebStateList* web_state_list,
-    web::WebState* old_web_state,
-    web::WebState* new_web_state,
-    int index) {
-  SetWebUsageEnabled(new_web_state, tab_model_.webUsageEnabled);
-}