Makes DockedWindowLayoutManager::UpdateDockBounds() handle null shelf_

ash/common/wm/dock/docked_window_layout_manager.cc

 // Copyright (c) 2013 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.
 
 #include "ash/common/wm/dock/docked_window_layout_manager.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/wm_shelf.h"
 #include "ash/common/shelf/wm_shelf_observer.h"
@@ skipping 1282 matching lines @@
       dock_container_->GetBounds().y(), dock_inset, work_area.height());
   docked_bounds_ =
       bounds + dock_container_->GetBoundsInScreen().OffsetFromOrigin();
   FOR_EACH_OBSERVER(DockedWindowLayoutManagerObserver, observer_list_,
                     OnDockBoundsChanging(bounds, reason));
   // Show or hide background for docked area.
   gfx::Rect background_bounds(docked_bounds_);
   if (shelf_observer_)
     background_bounds.Subtract(shelf_observer_->shelf_bounds_in_screen());
   if (docked_width > 0) {
-    if (!background_widget_)
-      background_widget_.reset(new DockedBackgroundWidget(this));
-    background_widget_->SetBackgroundBounds(background_bounds, alignment_);
-    background_widget_->Show();
+    // TODO: |shelf_| should not be null by the time we get here, but it may
+    // be in mash as startup sequence doesn't yet match that of ash. Once
+    // |shelf_| is created at same time as ash we can remove conditional.
+    // http://crbug.com/632099
+    if (shelf_) {
+      if (!background_widget_)
+        background_widget_.reset(new DockedBackgroundWidget(this));
+      background_widget_->SetBackgroundBounds(background_bounds, alignment_);
+      background_widget_->Show();
+    }
   } else if (background_widget_) {
     background_widget_->Hide();
   }
 }
 
 void DockedWindowLayoutManager::UpdateStacking(WmWindow* active_window) {
   if (!active_window) {
     if (!last_active_window_)
       return;
     active_window = last_active_window_;
@@ skipping 49 matching lines @@
 
 void DockedWindowLayoutManager::OnKeyboardBoundsChanging(
     const gfx::Rect& keyboard_bounds) {
   // This bounds change will have caused a change to the Shelf which does not
   // propagate automatically to this class, so manually recalculate bounds.
   Relayout();
   UpdateDockBounds(DockedWindowLayoutManagerObserver::KEYBOARD_BOUNDS_CHANGING);
 }
 
 }  // namespace ash