chromeos: Refactor shelf to create ShelfView earlier in startup

ash/public/interfaces/shelf.mojom

Index: ash/public/interfaces/shelf.mojom
diff --git a/ash/public/interfaces/shelf.mojom b/ash/public/interfaces/shelf.mojom
index 10127072e8934aa5737e124cc0ed9ba2eb746219..a630baf7e115dddde3eb277a512f6d27afdcba43 100644
--- a/ash/public/interfaces/shelf.mojom
+++ b/ash/public/interfaces/shelf.mojom
@@ -73,7 +73,9 @@ interface ShelfController {
 
 // ShelfObserver is notified on shelf changes; used to persist profile settings.
 interface ShelfObserver {
-  OnShelfCreated(int64 display_id);
+  // TODO(jamescook): Eliminate all these methods and use the ash pref service
+  // to observe and to set prefs.

[James Cook, 2017/05/16 21:32:35]

I think this could dramatically simplify ash/chrome communication. It doesn't
fully work in mash (e.g. crbug.com/721961)

[msw, 2017/05/16 22:41:59]

Acknowledged. Maybe file a bug to track that idea and cite it here?

[James Cook, 2017/05/17 16:16:12]

Done.

+  OnShelfInitialized(int64 display_id);
   OnAlignmentChanged(ShelfAlignment alignment, int64 display_id);
   OnAutoHideBehaviorChanged(ShelfAutoHideBehavior auto_hide, int64 display_id);
 };