ash: Reorder shutdown of ShelfLayoutManager and StatusAreaWidget

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index ff95424866e43eb71462d8b27f3d071040a14ef6..1d4aeeacc37e0faf3c2c7e07c9d47ece050fe5a5 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -261,6 +261,9 @@ ShelfLayoutManager::~ShelfLayoutManager() {
 }
 
 void ShelfLayoutManager::PrepareForShutdown() {
+  if (in_shutdown_)
+    return;
+  in_shutdown_ = true;

[oshima, 2016/05/24 20:49:10]

did you actually need this? resetting/removing observer seems to work just fine.

[James Cook, 2016/05/24 21:18:14]

I will need the in_shutdown_ variable in a future CL, but I don't need the if().
I've removed both and I will add back the variable in the next CL.

   // Clear all event filters, otherwise sometimes those filters may catch
   // synthesized mouse event and cause crashes during the shutdown.
   set_workspace_controller(NULL);