Keep track of accessibility focus across windows.

ui/views/accessibility/ax_aura_obj_cache.h

Index: ui/views/accessibility/ax_aura_obj_cache.h
diff --git a/ui/views/accessibility/ax_aura_obj_cache.h b/ui/views/accessibility/ax_aura_obj_cache.h
index 1129c1d237a8dde51e796c9bcc57eb4f122db7be..1e54de78e1971258c190cfc6fc7ac1b0bac1e43e 100644
--- a/ui/views/accessibility/ax_aura_obj_cache.h
+++ b/ui/views/accessibility/ax_aura_obj_cache.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "ui/aura/client/focus_change_observer.h"
 #include "ui/views/views_export.h"
 
 namespace base {
@@ -18,6 +19,9 @@ template <typename T> struct DefaultSingletonTraits;
 }
 
 namespace aura {
+namespace client {
+class FocusClient;
+}
 class Window;
 }  // namespace aura
 
@@ -27,7 +31,8 @@ class View;
 class Widget;
 
 // A cache responsible for assigning id's to a set of interesting Aura views.
-class VIEWS_EXPORT AXAuraObjCache {
+class VIEWS_EXPORT AXAuraObjCache
+    : public aura::client::FocusChangeObserver {
  public:
   // Get the single instance of this class.
   static AXAuraObjCache* GetInstance();
@@ -63,6 +68,9 @@ class VIEWS_EXPORT AXAuraObjCache {
   // Get all top level windows this cache knows about.
   void GetTopLevelWindows(std::vector<AXAuraObjWrapper*>* children);
 
+  // Get the object that has focus.
+  AXAuraObjWrapper* GetFocus();
+
   // Indicates if this object's currently being destroyed.
   bool is_destroying() { return is_destroying_; }
 
@@ -70,7 +78,13 @@ class VIEWS_EXPORT AXAuraObjCache {
   friend struct base::DefaultSingletonTraits<AXAuraObjCache>;
 
   AXAuraObjCache();
-  virtual ~AXAuraObjCache();
+  ~AXAuraObjCache() override;
+
+  View* GetFocusedView();
+
+  // aura::client::FocusChangeObserver override.
+  void OnWindowFocused(aura::Window* gained_focus,
+                       aura::Window* lost_focus) override;
 
   template <typename AuraViewWrapper, typename AuraView>
   AXAuraObjWrapper* CreateInternal(
@@ -93,6 +107,8 @@ class VIEWS_EXPORT AXAuraObjCache {
   std::map<int32_t, AXAuraObjWrapper*> cache_;
   int32_t current_id_;
 
+  aura::client::FocusClient* focus_client_;
+
   // True immediately when entering this object's destructor.
   bool is_destroying_;