arc-a11y: Update obsolete code comments

Recent changes simplified AXTreeSourceArc::NotifyAccessibilityEvent, but
some code comments were not updated.
This change updates them.

Bug: none
Test: build passes.
Change-Id: I3da87a03700c96c15f94b439266935dbfd8fbb2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2259532
Auto-Submit: Hiroki Sato <hirokisato@chromium.org>
Commit-Queue: Sara Kato <sarakato@chromium.org>
Reviewed-by: Sara Kato <sarakato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781177}

chrome/browser/chromeos/arc/accessibility/ax_tree_source_arc.cc

@@ -64,12 +64,7 @@ void AXTreeSourceArc::NotifyAccessibilityEvent(AXEventData* event_data) {
   is_notification_ = event_data->notification_key.has_value();
   is_input_method_window_ = event_data->is_input_method_window;
 
-  // The following loops perform caching to prepare for AXTreeSerializer.
-  // First, we cache the windows.
-  // Next, we cache the nodes. To compute importance table, we want a mapping
-  // from node id to an index in event_data->node_data is needed to avoid O(N^2)
-  // computation, iterate it twice.
-  // Finally, we cache each node's computed bounds, based on its descendants.
+  // Prepare the wrapper objects of mojom data from Android.
   CHECK(event_data->window_data);
   root_id_ = event_data->window_data->at(0)->window_id;
   for (size_t i = 0; i < event_data->window_data->size(); ++i) {
@@ -106,6 +101,7 @@ void AXTreeSourceArc::NotifyAccessibilityEvent(AXEventData* event_data) {
     }
   }
 
+  // Compute each node's bounds, based on its descendants.
   // Assuming |nodeData| is in pre-order, compute cached bounds in post-order to
   // avoid an O(n^2) amount of work as the computed bounds uses descendant
   // bounds.