Now that the launcher is sized to the width of the root window we need

ui/aura_shell/shelf_layout_manager.h

Index: ui/aura_shell/shelf_layout_manager.h
diff --git a/ui/aura_shell/shelf_layout_manager.h b/ui/aura_shell/shelf_layout_manager.h
index 21a9b6d7c2abfcb4b34d90cdc034d8db27621830..f2be1886df1558f23286e53b51383e2bff3cee13 100644
--- a/ui/aura_shell/shelf_layout_manager.h
+++ b/ui/aura_shell/shelf_layout_manager.h
@@ -21,10 +21,12 @@ class Widget;
 namespace aura_shell {
 namespace internal {
 
-// ShelfLayoutManager is a layout manager responsible for the launcher.
-// Also supports showing and hiding the launcher/status area
-// as well as positioning them.
-// Exported for unit tests.
+// ShelfLayoutManager is the layout manager responsible for the launcher and
+// status widgets. The launcher is given the total available width and told the
+// width of the status area. This allows the launcher to draw the background and
+// layout to the status area.
+// To respond to bounds changes in the status area StatusAreaLayoutManager works
+// closely with ShelfLayoutManager.
 class AURA_SHELL_EXPORT ShelfLayoutManager : public aura::LayoutManager,
                                              public ui::LayerAnimationObserver {
  public: