Make GetWindowId to return an optional

Follow-up of crrev/c/1903171 to make GetWindowID() return an
optional. The window_id variable is also an optional.

Bug: None (follow-up CL)
Test: Do not observe crash in crbug/1020413
Change-Id: Ic3dd6a009871c725bbb97e0a565d7eec84e7c362
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930532
Commit-Queue: Sara Kato <sarakato@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Sara Kato <sarakato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719458}

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

@@ -581,10 +581,10 @@ void ArcAccessibilityHelperBridge::OnAction(
   if (!tree_source)
     return;
 
-  const int window_id = tree_source->GetWindowId();
-  if (window_id == ui::AXNode::kInvalidAXID)
+  base::Optional<int32_t> window_id = tree_source->window_id();
+  if (!window_id)
     return;
-  action_data->window_id = window_id;
+  action_data->window_id = window_id.value();
 
   switch (data.action) {
     case ax::mojom::Action::kDoDefault:

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

@@ -255,14 +255,6 @@ bool AXTreeSourceArc::IsRootOfNodeTree(int32_t id) const {
   return !parent_tree_it->second->IsNode();
 }
 
-int32_t AXTreeSourceArc::GetWindowId() const {
-  if (window_id_.has_value())
-    return *window_id_;
-  // |window_id_| could be empty when called after OnNotificationStateChanged,
-  // but before OnAccessibilityEvent in ArcAccessibilityHelperBridge.
-  return ui::AXNode::kInvalidAXID;
-}
-
 bool AXTreeSourceArc::GetTreeData(ui::AXTreeData* data) const {
   data->tree_id = ax_tree_id();
   if (focused_id_.has_value())

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

@@ -73,9 +73,6 @@ class AXTreeSourceArc : public ui::AXTreeSource<AccessibilityInfoDataWrapper*,
   // parent window).
   bool IsRootOfNodeTree(int32_t id) const;
 
-  // Gets the window id of this tree.
-  int32_t GetWindowId() const;
-
   // AXTreeSource:
   bool GetTreeData(ui::AXTreeData* data) const override;
   AccessibilityInfoDataWrapper* GetRoot() const override;
@@ -89,6 +86,9 @@ class AXTreeSourceArc : public ui::AXTreeSource<AccessibilityInfoDataWrapper*,
 
   bool is_input_method_window() { return is_input_method_window_; }
 
+  // The window id of this tree.
+  base::Optional<int32_t> window_id() const { return window_id_; }
+
  private:
   friend class arc::AXTreeSourceArcTest;