Fix incorrect use of AXState caused when refactoring two enums into one.

ui/views/controls/button/checkbox.cc

Index: ui/views/controls/button/checkbox.cc
diff --git a/ui/views/controls/button/checkbox.cc b/ui/views/controls/button/checkbox.cc
index 2389b62bbf43c9b326b3697a6372a0a3ff77065a..c8a06823c7e24c3cc6268ffaeb8efc3996688d54 100644
--- a/ui/views/controls/button/checkbox.cc
+++ b/ui/views/controls/button/checkbox.cc
@@ -97,7 +97,8 @@ const char* Checkbox::GetClassName() const {
 void Checkbox::GetAccessibleState(ui::AXViewState* state) {
   LabelButton::GetAccessibleState(state);
   state->role = ui::AX_ROLE_CHECK_BOX;
-  state->state = checked() ? ui::AX_STATE_CHECKED : 0;
+  if (checked())
+    state->SetStateFlag(ui::AX_STATE_CHECKED);
 }
 
 void Checkbox::OnFocus() {