Use the correct BrowserAccessibilityManager for a node

No change in behavior expected, but this is to fix an inconsistency in
the code where calls were made using a mismatched BrowserAccessibility
and BrowserAccessibilityManager.

Bug: None
Change-Id: I73cac6b0e901c2685272415fcb28c7542ed6fe34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615201Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841554}

content/browser/accessibility/browser_accessibility_manager.cc

@@ -357,9 +357,11 @@ void BrowserAccessibilityManager::ParentConnectionChanged(
     return;
   parent->OnDataChanged();
   parent->UpdatePlatformAttributes();
-  parent =
-      RetargetForEvents(parent, RetargetEventType::RetargetEventTypeGenerated);
-  FireGeneratedEvent(ui::AXEventGenerator::Event::CHILDREN_CHANGED, parent);
+  BrowserAccessibilityManager* parent_manager = parent->manager();
+  parent = parent_manager->RetargetForEvents(
+      parent, RetargetEventType::RetargetEventTypeGenerated);
+  parent_manager->FireGeneratedEvent(
+      ui::AXEventGenerator::Event::CHILDREN_CHANGED, parent);
 }
 
 BrowserAccessibility* BrowserAccessibilityManager::GetPopupRoot() const {

content/browser/accessibility/browser_accessibility_manager.h

@@ -196,6 +196,9 @@ class CONTENT_EXPORT BrowserAccessibilityManager : public ui::AXTreeObserver,
   // If this tree has a parent tree, return the parent node in that tree.
   BrowserAccessibility* GetParentNodeFromParentTree() const;
 
+  // Refreshes a parent node in a parent tree when it needs to be informed that
+  // this tree is ready or being destroyed. For example, an iframe object
+  // in a parent tree may need to link or unlink to this manager.
   void ParentConnectionChanged(BrowserAccessibility* parent);
 
   // In general, there is only a single node with the role of kRootWebArea,