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/+/1938489Reviewed-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}

content/browser/accessibility/browser_accessibility_manager.cc

@@ -342,20 +342,12 @@ void BrowserAccessibilityManager::OnWindowBlurred() {
     SetLastFocusedNode(nullptr);
 }
 
-void BrowserAccessibilityManager::UserIsNavigatingAway() {
-  user_is_navigating_away_ = true;
-}
-
 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::DidStartLoading() {
+  user_is_navigating_away_ = true;
 }
 
 void BrowserAccessibilityManager::DidStopLoading() {

content/browser/accessibility/browser_accessibility_manager.h

@@ -191,14 +191,16 @@ class CONTENT_EXPORT BrowserAccessibilityManager : public ui::AXTreeObserver,
   // view lost focus.
   virtual void OnWindowBlurred();
 
-  // Notify the accessibility manager about page navigation.
-  // 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();
+
+  // 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;
   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

@@ -4484,20 +4484,6 @@ 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(),
@@ -5982,15 +5968,6 @@ 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() {