Fix ASan WidgetTest.WidgetDestroyedItselfDoesNotCrash crash.

This makes sure WidgetTest.WidgetDestroyedItselfDoesNotCrash test does NOT
crash with use-after-free ASan error in ChromeOS and Mac. Test was added in
https://chromium-review.googlesource.com/c/chromium/src/+/1145261/ and only
covered Windows and Linux.

Bug: 878314

Change-Id: Ifde7f402955bd34bfd0618e4f67c52feeb333624
Reviewed-on: https://chromium-review.googlesource.com/1193283
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586678}

ui/views/widget/native_widget_aura.cc

@@ -895,8 +895,12 @@ void NativeWidgetAura::OnWindowDestroying(aura::Window* window) {
 
 void NativeWidgetAura::OnWindowDestroyed(aura::Window* window) {
   window_ = NULL;
+  // |OnNativeWidgetDestroyed| may delete |this| if the object does not own
+  // itself.
+  bool should_delete_this =
+      (ownership_ == Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET);
   delegate_->OnNativeWidgetDestroyed();
-  if (ownership_ == Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET)
+  if (should_delete_this)
     delete this;
 }
 

ui/views/widget/native_widget_mac.mm

@@ -114,8 +114,12 @@ void NativeWidgetMac::WindowDestroying() {
 void NativeWidgetMac::WindowDestroyed() {
   DCHECK(bridge());
   bridge_host_.reset();
+  // |OnNativeWidgetDestroyed| may delete |this| if the object does not own
+  // itself.
+  bool should_delete_this =
+      (ownership_ == Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET);
   delegate_->OnNativeWidgetDestroyed();
-  if (ownership_ == Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET)
+  if (should_delete_this)
     delete this;
 }