Fix shelf alignment and auto-hide initialization.

ash/common/shelf/wm_shelf.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_COMMON_SHELF_WM_SHELF_H_
 #define ASH_COMMON_SHELF_WM_SHELF_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 144 matching lines @@
   // Layout manager for the shelf container window. Instances are constructed by
   // ShelfWidget and lifetimes are managed by the container windows themselves.
   ShelfLayoutManager* shelf_layout_manager_ = nullptr;
 
   std::unique_ptr<ShelfWidget> shelf_widget_;
 
   // Internal implementation detail. Do not expose externally. Owned by views
   // hierarchy. Null before login and in secondary display init.
   ShelfView* shelf_view_ = nullptr;
 
+  // These initial values hide the shelf until user preferences are available.
   ShelfAlignment alignment_ = SHELF_ALIGNMENT_BOTTOM_LOCKED;
+  ShelfAutoHideBehavior auto_hide_behavior_ = SHELF_AUTO_HIDE_ALWAYS_HIDDEN;

[James Cook, 2017/02/14 01:38:03]

This makes me a bit nervous. It's probably fine, but could you make sure you've
tested a couple cases manually before landing this CL? Specifically I'm worried
about:
* OOBE (run --login-manager with empty profile dir)
* Supervised user creation (using the ... in the fake shelf at login)

If those are OK then I'm good with this.

[msw, 2017/02/14 05:13:18]

Done. I had already run OOBE with an existing account; I also tried a new
account. (when signing in to an existing account with a non-bottom shelf pref,
we use the bottom alignment (and blank wallpaper) for a short time, before the
cloud prefs are loaded).

Hmm, supervised users don't have the option of changing the shelf alignment, but
that also seems to be the case on ToT. Perhaps that's intentional, or perhaps
they're already getting stuck in SHELF_ALIGNMENT_BOTTOM_LOCKED after login.
Relatedly, I wasn't able to test "Browse as Guest" manually, because it has an
unrelated login crash. Do you think I should dig in more here for this CL?

 
   // Sets shelf alignment to bottom during login and screen lock.
   std::unique_ptr<ShelfLockingManager> shelf_locking_manager_;
 
-  ShelfAutoHideBehavior auto_hide_behavior_ = SHELF_AUTO_HIDE_BEHAVIOR_NEVER;
-
   base::ObserverList<WmShelfObserver> observers_;
 
   // Forwards mouse and gesture events to ShelfLayoutManager for auto-hide.
   // TODO(mash): Facilitate simliar functionality in mash: crbug.com/631216
   std::unique_ptr<AutoHideEventHandler> auto_hide_event_handler_;
 
   // Forwards touch gestures on a bezel sensor to the shelf.
   // TODO(mash): Facilitate simliar functionality in mash: crbug.com/636647
   std::unique_ptr<ShelfBezelEventHandler> bezel_event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(WmShelf);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_WM_SHELF_H_