arc-a11y: Fix focus computation in non full focus mode

We introduced full focus mode to simulate TalkBack's focusability
and announcement computation.
AXTreeSourceArc.FindFirstFocusableNode() uses
AccessibilityNodeInfoWrapper.IsAccessibilityFocusableContainer(), which
expects to be in the full focus mode.

This fixes usages of FindFirstFocusableNode() so that the magnifier's
focus following feature works well in ARC++ apps.

AX-Relnotes: None. Fix of regression.
Bug: b:175362381
Test: manual. In PlayStore, magnifier correctly follows the focus.
Change-Id: I0d000e2009137a68f8bd1cf6cbaac45cf087b834
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586499Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Sara Kato <sarakato@chromium.org>
Commit-Queue: Hiroki Sato <hirokisato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836517}

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

@@ -419,7 +419,8 @@ bool AXTreeSourceArc::UpdateAndroidFocusedId(const AXEventData& event_data) {
     if (source_node && source_node->IsVisibleToUser()) {
       // Sometimes Android sets focus on unfocusable node, e.g. ListView.
       AccessibilityInfoDataWrapper* adjusted_node =
-          FindFirstFocusableNode(source_node);
+          UseFullFocusMode() ? FindFirstFocusableNode(source_node)
+                             : source_node;
       if (IsValid(adjusted_node))
         android_focused_id_ = adjusted_node->GetId();
     }
@@ -466,7 +467,7 @@ bool AXTreeSourceArc::UpdateAndroidFocusedId(const AXEventData& event_data) {
       new_focus = GetFromId(itr->second);
 
     // Otherwise, try focus on the first focusable node.
-    if (!IsValid(new_focus))
+    if (!IsValid(new_focus) && UseFullFocusMode())
       new_focus = FindFirstFocusableNode(GetFromId(event_data.source_id));
 
     if (IsValid(new_focus))

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

@@ -713,6 +713,8 @@ TEST_F(AXTreeSourceArcTest, OnViewSelectedEvent) {
 }
 
 TEST_F(AXTreeSourceArcTest, OnWindowStateChangedEvent) {
+  set_full_focus_mode(true);
+
   auto event = AXEventData::New();
   event->task_id = 1;
 
@@ -805,6 +807,8 @@ TEST_F(AXTreeSourceArcTest, OnWindowStateChangedEvent) {
 }
 
 TEST_F(AXTreeSourceArcTest, OnFocusEvent) {
+  set_full_focus_mode(true);
+
   auto event = AXEventData::New();
   event->task_id = 1;
   event->event_type = AXEventType::VIEW_FOCUSED;
@@ -858,7 +862,6 @@ TEST_F(AXTreeSourceArcTest, OnFocusEvent) {
 
   // VIEW_ACCESSIBILITY_FOCUSED event also updates the focus in screen reader
   // mode.
-  set_full_focus_mode(true);
   SetProperty(node1, AXBooleanProperty::ACCESSIBILITY_FOCUSED, false);
   SetProperty(node2, AXBooleanProperty::ACCESSIBILITY_FOCUSED, true);
   event->event_type = AXEventType::VIEW_ACCESSIBILITY_FOCUSED;