Clear class properties in ~View

This lets us make sure that the View (but not necessarily subclasses)
outlive their properties. Without this change accessing View in the
property destructor would be a use after free.

Bug: None
Change-Id: I8e783fbf46ed046bd2ac7e77ed2373c1da5758e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1828217Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Auto-Submit: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700483}

ui/views/view.cc

@@ -143,6 +143,12 @@ View::~View() {
 
   for (ui::Layer* layer_beneath : layers_beneath_)
     layer_beneath->RemoveObserver(this);
+
+  // Clearing properties explicitly here lets us guarantee that properties
+  // outlive |this| (at least the View part of |this|). This is intentionally
+  // called at the end so observers can examine properties inside
+  // OnViewIsDeleting(), for instance.
+  ClearProperties();
 }
 
 // Tree operations -------------------------------------------------------------