ash: Fix setting the tray-widget size when tray-view for date changes.

ash/system/date/date_view.cc

Index: ash/system/date/date_view.cc
diff --git a/ash/system/date/date_view.cc b/ash/system/date/date_view.cc
index 6c614bb5787fc696c0f80201678040102a516f3b..f303f73a37c383c77e9f948ceead97c2edb9ebfb 100644
--- a/ash/system/date/date_view.cc
+++ b/ash/system/date/date_view.cc
@@ -62,11 +62,6 @@ void BaseDateTimeView::UpdateText() {
   base::Time now = base::Time::Now();
   gfx::Size old_size = GetPreferredSize();
   UpdateTextInternal(now);
-  if (GetWidget() && GetPreferredSize() != old_size) {
-    // Forcing the widget to the new size is sufficient. The positioning is
-    // taken care of by the layout manager (ShelfLayoutManager).
-    GetWidget()->SetSize(GetPreferredSize());
-  }
   SchedulePaint();
 
   // Try to set the timer to go off at the next change of the minute. We don't
@@ -94,6 +89,12 @@ void BaseDateTimeView::UpdateText() {
 BaseDateTimeView::BaseDateTimeView() {
 }
 
+void BaseDateTimeView::ChildPreferredSizeChanged(views::View* child) {
+  views::View::PreferredSizeChanged();
+  if (GetWidget())
+    GetWidget()->SetSize(GetWidget()->GetContentsView()->GetPreferredSize());
+}
+
 void BaseDateTimeView::OnLocaleChanged() {
   UpdateText();
 }