Fix TalkBack fallback keyboard shortcut

- Update window properties and detach ax child tree when user switches
  back to TalkBack.

  ]. Confirm that TalkBack works well.

Bug: 881695
Test: Open any android app with spoken feedback and press Search+A then
Change-Id: I2b5db2d77e49e674e98c1b3cfbb18b2567d69388
Reviewed-on: https://chromium-review.googlesource.com/1212210Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Yuki Awano <yawano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590136}

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

@@ -159,20 +159,43 @@ void ArcAccessibilityHelperBridge::SetNativeChromeVoxArcSupport(bool enabled) {
   if (task_id == kNoTaskId)
     return;
 
+  std::unique_ptr<aura::WindowTracker> window_tracker =
+      std::make_unique<aura::WindowTracker>();
+  window_tracker->Add(window);
+
   auto* instance =
       ARC_GET_INSTANCE_FOR_METHOD(arc_bridge_service_->accessibility_helper(),
                                   SetNativeChromeVoxArcSupportForFocusedWindow);
   instance->SetNativeChromeVoxArcSupportForFocusedWindow(
       enabled, base::BindOnce(&ArcAccessibilityHelperBridge::
                                   OnSetNativeChromeVoxArcSupportProcessed,
-                              base::Unretained(this), enabled));
+                              base::Unretained(this), std::move(window_tracker),
+                              enabled));
 }
 
 void ArcAccessibilityHelperBridge::OnSetNativeChromeVoxArcSupportProcessed(
+    std::unique_ptr<aura::WindowTracker> window_tracker,
     bool enabled,
     bool processed) {
-  if (!enabled)
-    task_id_to_tree_.clear();
+  if (!processed || window_tracker->windows().size() != 1)
+    return;
+
+  aura::Window* window = window_tracker->Pop();
+  int32_t task_id = GetTaskId(window);
+  DCHECK_NE(task_id, kNoTaskId);
+
+  if (!enabled) {
+    task_id_to_tree_.erase(task_id);
+
+    exo::Surface* surface = exo::ShellSurfaceBase::GetMainSurface(window);
+    if (surface) {
+      views::Widget* widget = views::Widget::GetWidgetForNativeWindow(window);
+      static_cast<exo::ShellSurfaceBase*>(widget->widget_delegate())
+          ->SetChildAxTreeId(kInvalidTreeId);
+    }
+  }
+
+  UpdateWindowProperties(window);
 }
 
 void ArcAccessibilityHelperBridge::Shutdown() {
@@ -264,8 +287,7 @@ void ArcAccessibilityHelperBridge::OnAccessibilityEvent(
         if (surface) {
           views::Widget* widget =
               views::Widget::GetWidgetForNativeWindow(active_window);
-          static_cast<exo::ShellSurfaceBase*>(
-              widget->widget_delegate()->GetContentsView())
+          static_cast<exo::ShellSurfaceBase*>(widget->widget_delegate())
               ->SetChildAxTreeId(tree_data.tree_id);
         }
       }

chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge.h

@@ -18,6 +18,7 @@
 #include "components/arc/connection_observer.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "ui/accessibility/ax_host_delegate.h"
+#include "ui/aura/window_tracker.h"
 #include "ui/wm/public/activation_change_observer.h"
 
 class Profile;
@@ -56,7 +57,10 @@ class ArcAccessibilityHelperBridge
   void SetNativeChromeVoxArcSupport(bool enabled);
 
   // Receives the result of setting native ChromeVox Arc support.
-  void OnSetNativeChromeVoxArcSupportProcessed(bool enabled, bool processed);
+  void OnSetNativeChromeVoxArcSupportProcessed(
+      std::unique_ptr<aura::WindowTracker> window_tracker,
+      bool enabled,
+      bool processed);
 
   // KeyedService overrides.
   void Shutdown() override;

components/exo/shell_surface_base.cc

@@ -502,10 +502,6 @@ void ShellSurfaceBase::SetStartupId(const char* startup_id) {
 }
 
 void ShellSurfaceBase::SetChildAxTreeId(int32_t child_ax_tree_id) {
-  // We don't expect that child ax tree id is changed once it's set.
-  DCHECK_EQ(child_ax_tree_id_, kInvalidChildAxTreeId);
-  DCHECK_NE(child_ax_tree_id, kInvalidChildAxTreeId);
-
   child_ax_tree_id_ = child_ax_tree_id;
 
   this->NotifyAccessibilityEvent(ax::mojom::Event::kChildrenChanged, false);