Fix shelf alignment and auto-hide initialization.

ash/common/shelf/wm_shelf.h

Index: ash/common/shelf/wm_shelf.h
diff --git a/ash/common/shelf/wm_shelf.h b/ash/common/shelf/wm_shelf.h
index ee88e94b1525b44d9b1dd9bcec0e70e3596a4705..f63148baf201dcd1ae43c52472c44decf580c036 100644
--- a/ash/common/shelf/wm_shelf.h
+++ b/ash/common/shelf/wm_shelf.h
@@ -162,13 +162,13 @@ class ASH_EXPORT WmShelf : public ShelfLayoutManagerObserver {
   // 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.