Fix a crash in AutofillPopupViewNativeViews.

RemoveAllChildViews() deletes all the child views, thus, turning some members
holding dangling pointers. The code should NULL them.

Bug: 1023941
Change-Id: I642cff0f1a22e0c894fe4a46421a91182d662c15
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1914364Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715008}

chrome/browser/ui/views/autofill/autofill_popup_view_native_views.cc

@@ -940,6 +940,9 @@ base::Optional<int32_t> AutofillPopupViewNativeViews::GetAxUniqueId() {
 void AutofillPopupViewNativeViews::CreateChildViews() {
   RemoveAllChildViews(true /* delete_children */);
   rows_.clear();
+  scroll_view_ = nullptr;
+  body_container_ = nullptr;
+  footer_container_ = nullptr;
 
   int line_number = 0;
   bool has_footer = false;