Only defer accessibility events from the main frame.

This is just a mitigation in case we need it,
I am still investigating to see if there is a
better solution.
CL that introduced regression:

https: //chromium-review.googlesource.com/c/chromium/src/+/2219098
Bug: 1110068
Change-Id: Ib69395ea6ebe56183a9e39d1696ea42c64411b79
AX-Relnotes: n/a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2328051Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Jacques Newman <janewman@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#794742}

content/renderer/accessibility/render_accessibility_impl.cc

@@ -222,6 +222,11 @@ RenderAccessibilityImpl::RenderAccessibilityImpl(
   settings->SetAriaModalPrunesAXTree(true);
 #endif
 
+  if (render_frame_->IsMainFrame())
+    event_schedule_mode_ = EventScheduleMode::kDeferEvents;
+  else
+    event_schedule_mode_ = EventScheduleMode::kProcessEventsImmediately;
+
   const WebDocument& document = GetMainDocument();
   if (!document.IsNull()) {
     ax_context_ = std::make_unique<WebAXContext>(document);

content/renderer/accessibility/render_accessibility_impl.h

@@ -297,8 +297,8 @@ class CONTENT_EXPORT RenderAccessibilityImpl : public RenderAccessibility,
   // (only when debugging flags are enabled, never under normal circumstances).
   bool has_injected_stylesheet_ = false;
 
-  // We defer events to improve performance durung the initial page load.
-  EventScheduleMode event_schedule_mode_ = EventScheduleMode::kDeferEvents;
+  // We defer events to improve performance during the initial page load.
+  EventScheduleMode event_schedule_mode_;
 
   // Whether we should highlight annotation results visually on the page
   // for debugging.