chromeos: Refactor shelf to create ShelfView earlier in startup

ash/shelf/shelf_widget.h

Index: ash/shelf/shelf_widget.h
diff --git a/ash/shelf/shelf_widget.h b/ash/shelf/shelf_widget.h
index 0b9097cccf47199ab82189f78897c7bd481cb4d1..66d5d4759b33ead87de7e290ed9a2232968423a5 100644
--- a/ash/shelf/shelf_widget.h
+++ b/ash/shelf/shelf_widget.h
@@ -58,13 +58,8 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   ShelfLayoutManager* shelf_layout_manager() { return shelf_layout_manager_; }
   StatusAreaWidget* status_area_widget() const { return status_area_widget_; }
 
-  // Creates the shelf view and populates it with icons. Called after the user
-  // session is active (and hence the user profile is available).
-  ShelfView* CreateShelfView();
   void PostCreateShelf();
 
-  bool IsShelfVisible() const;
-
   bool IsShowingAppList() const;
   bool IsShowingContextMenu() const;
   bool IsShowingOverflowBubble() const;
@@ -101,6 +96,9 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   // ShelfLayoutManagerObserver overrides:
   void WillDeleteShelfLayoutManager() override;
 
+  // Internal implementation detail. Do not expose outside of tests.
+  ShelfView* shelf_view_for_testing() const { return shelf_view_; }
+
  private:
   class DelegateView;
   friend class DelegateView;
@@ -116,9 +114,8 @@ class ASH_EXPORT ShelfWidget : public views::Widget,
   // |delegate_view_| is the contents view of this widget and is cleaned up
   // during CloseChildWindows of the associated RootWindowController.
   DelegateView* delegate_view_;
-  // View containing the shelf items. Owned by the views hierarchy. Null when
-  // at the login screen.
-  ShelfView* shelf_view_;
+  // View containing the shelf items. Owned by the views hierarchy.
+  ShelfView* const shelf_view_;
   ShelfBackgroundAnimator background_animator_;
   bool activating_as_fallback_;