[Toolbar container] Destroy potential observers before the observer list

This CL makes sure ToolbarIconContainerView destroys its children before
its own observer list (this is needed so that childred that observe
ToolbarIconContainerView can remove themselves from the observer list).

Bug: 1013418
Change-Id: Ica6b8c89b9d0683933c84d65faf6f9a4641e55b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860339Reviewed-by: Peter Boström <pbos@chromium.org>
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705628}

chrome/browser/ui/views/toolbar/toolbar_icon_container_view.cc

@@ -29,7 +29,11 @@ ToolbarIconContainerView::ToolbarIconContainerView(bool uses_highlight)
                   gfx::Insets(0, GetLayoutConstant(TOOLBAR_ELEMENT_PADDING)));
 }
 
-ToolbarIconContainerView::~ToolbarIconContainerView() = default;
+ToolbarIconContainerView::~ToolbarIconContainerView() {
+  // As childred might be Observers of |this|, we need to destroy them before
+  // destroying |observers_|.
+  RemoveAllChildViews(true);
+}
 
 void ToolbarIconContainerView::UpdateAllIcons() {}