[ash-md] Fixed TriView to relayout child Views when their preferred size changed.

ash/common/system/tray/tri_view.cc

Index: ash/common/system/tray/tri_view.cc
diff --git a/ash/common/system/tray/tri_view.cc b/ash/common/system/tray/tri_view.cc
index ea2ca9327d8fc3a902f91dbca1a7114bd81c77b9..c71666f681bc39b58d5c72e550d78e0ccccd674a 100644
--- a/ash/common/system/tray/tri_view.cc
+++ b/ash/common/system/tray/tri_view.cc
@@ -27,6 +27,18 @@ views::BoxLayout::Orientation GetOrientation(TriView::Orientation orientation) {
   return views::BoxLayout::kHorizontal;
 }
 
+// A View that will perform a layout if a child view's preferred size changes.
+class RelayoutView : public views::View {

[tdanderson, 2016/11/28 21:47:37]

Hm, I'm a bit surprised there isn't something like this in use somewhere else
already.

+ public:
+  RelayoutView() {}
+
+  // views::View:
+  void ChildPreferredSizeChanged(View* child) override { Layout(); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RelayoutView);
+};
+
 }  // namespace
 
 TriView::TriView() : TriView(0) {}
@@ -44,9 +56,9 @@ TriView::TriView(Orientation orientation, int padding_between_containers)
       start_container_layout_manager_(new SizeRangeLayout),
       center_container_layout_manager_(new SizeRangeLayout),
       end_container_layout_manager_(new SizeRangeLayout) {
-  AddChildView(new views::View);
-  AddChildView(new views::View);
-  AddChildView(new views::View);
+  AddChildView(new RelayoutView);
+  AddChildView(new RelayoutView);
+  AddChildView(new RelayoutView);
 
   GetContainer(Container::START)
       ->SetLayoutManager(GetLayoutManager(Container::START));