Revert "Notify BrowserAccessibilityManager via WebContentsObserver"

This reverts commit 0885c956.

Reason for revert: Unfortunately, this change results in the
notification of page-load-complete happening much later than it
did previously.

Since a11y events aren't fired when |user_is_navigating_away_|, the
result is that some events that occur early in a page's lifetime are
not emitted.  This is most visible for programmatic 'focus' changes;
if they're not emitted, any connected AT doesn't know the focus has
changed.

Original change's description:
> Notify BrowserAccessibilityManager via WebContentsObserver
>
> This is the last of a series of CLs that remove manual notifications
> BrowserAccessibilityManager, now that it implements WebContentsObserver.
> This CL removes manual BAM::Navigation{Succeeded,Failed} notifications
> in favor of WCO::DidFinishNavigation, and BAM::UserIsNavigatingAway in
> favor of WCO::DidStartLoading.
>
> Bug: 981271
> Change-Id: Ieca6ce0b97f2a0267fd7f2582ab1e333deb11b95
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1938489
> Reviewed-by: Matt Falkenhagen <falken@chromium.org>
> Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
> Commit-Queue: Dominic Farolino <dom@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#720102}

TBR=falken@chromium.org,dmazzoni@chromium.org,dom@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 981271
Change-Id: I41d68985b964792083aa5b6628bb3bc0972c9790
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2024154Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Ian Prest <iapres@microsoft.com>
Commit-Queue: Ian Prest <iapres@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#735980}

content/browser/accessibility/browser_accessibility_manager.cc

@@ -342,14 +342,22 @@ void BrowserAccessibilityManager::OnWindowBlurred() {
     SetLastFocusedNode(nullptr);
 }
 
-void BrowserAccessibilityManager::UserIsReloading() {
+void BrowserAccessibilityManager::UserIsNavigatingAway() {
   user_is_navigating_away_ = true;
 }
 
-void BrowserAccessibilityManager::DidStartLoading() {
+void BrowserAccessibilityManager::UserIsReloading() {
   user_is_navigating_away_ = true;
 }
 
+void BrowserAccessibilityManager::NavigationSucceeded() {
+  user_is_navigating_away_ = false;
+}
+
+void BrowserAccessibilityManager::NavigationFailed() {
+  user_is_navigating_away_ = false;
+}
+
 void BrowserAccessibilityManager::DidStopLoading() {
   user_is_navigating_away_ = false;
 }

content/browser/accessibility/browser_accessibility_manager.h

@@ -194,16 +194,14 @@ class CONTENT_EXPORT BrowserAccessibilityManager : public ui::AXTreeObserver,
   // view lost focus.
   virtual void OnWindowBlurred();
 
-  virtual void UserIsReloading();
-
-  // WebContentsObserver implementation.
   // Notify the accessibility manager about page navigation.
-  // BrowserAccessibilityManager used to be manually notified at the same time
-  // WebContentsObserver's DidStartLoading(), DidStopLoading(), and
-  // DidFinishNavigation() methods were called. Since then, it was determined
-  // BrowserAccessibilityManager does not need to distinguish between
-  // DidFinishNavigation() and DidStopLoading().
-  void DidStartLoading() override;
+  // TODO(domfarolino, dmazzoni): Implement WebContentsObserver methods that
+  // correspond to the ones we provide today, so we can stop being manually
+  // notified of navigation events when they happen.
+  void UserIsNavigatingAway();
+  virtual void UserIsReloading();
+  void NavigationSucceeded();
+  void NavigationFailed();
   void DidStopLoading() override;
 
   // Keep track of if this page is hidden by an interstitial, in which case

content/browser/web_contents/web_contents_impl.cc

@@ -4488,6 +4488,20 @@ void WebContentsImpl::DidFinishNavigation(NavigationHandle* navigation_handle) {
     display_cutout_host_impl_->DidFinishNavigation(navigation_handle);
 
   if (navigation_handle->HasCommitted()) {
+    // TODO(domfarolino, dmazzoni): Do this using WebContentsObserver. See
+    // https://crbug.com/981271.
+    BrowserAccessibilityManager* manager =
+        static_cast<RenderFrameHostImpl*>(
+            navigation_handle->GetRenderFrameHost())
+            ->browser_accessibility_manager();
+    if (manager) {
+      if (navigation_handle->IsErrorPage()) {
+        manager->NavigationFailed();
+      } else {
+        manager->NavigationSucceeded();
+      }
+    }
+
     if (navigation_handle->IsInMainFrame()) {
       last_committed_source_id_including_same_document_ =
           ukm::ConvertToSourceId(navigation_handle->GetNavigationId(),
@@ -5956,6 +5970,15 @@ void WebContentsImpl::DidStartLoading(FrameTreeNode* frame_tree_node,
   // Reset the focus state from DidStartNavigation to false if a new load starts
   // afterward, in case loading logic triggers a FocusLocationBarByDefault call.
   should_focus_location_bar_by_default_ = false;
+
+  // Notify accessibility that the user is navigating away from the
+  // current document.
+  // TODO(domfarolino, dmazzoni): Do this using WebContentsObserver. See
+  // https://crbug.com/981271.
+  BrowserAccessibilityManager* manager =
+      frame_tree_node->current_frame_host()->browser_accessibility_manager();
+  if (manager)
+    manager->UserIsNavigatingAway();
 }
 
 void WebContentsImpl::DidStopLoading() {