Check if the focused view is valid

ui/views/focus/focus_manager.cc

Index: ui/views/focus/focus_manager.cc
diff --git a/ui/views/focus/focus_manager.cc b/ui/views/focus/focus_manager.cc
index adb161201299926872ea8893ac17189b159576eb..b482dbe5128b40112ffb0572db11f019d819834f 100644
--- a/ui/views/focus/focus_manager.cc
+++ b/ui/views/focus/focus_manager.cc
@@ -301,6 +301,9 @@ void FocusManager::SetFocusedViewWithReason(
     View* view, FocusChangeReason reason) {
   if (focused_view_ == view)
     return;
+  // TODO(oshima|achuith): This is to diagnose crbug.com/687232.
+  // Change this to DCHECK once it's resolved.
+  CHECK(!view || ContainsView(view));
 
 #if !defined(OS_MACOSX)
   // TODO(warx): There are some AccessiblePaneViewTest failed on macosx.