Speculative ShelfView::GetTitleForView crash fix.

ash/shelf/shelf_view.cc

 // Copyright (c) 2012 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/shelf/shelf_view.h"
 
 #include <algorithm>
 #include <memory>
 
 #include "ash/ash_constants.h"
@@ skipping 524 matching lines @@
     return false;
   }
   const ShelfItem* item = ShelfItemForView(view);
   if (!item)
     return false;
   return item_manager_->GetShelfItemDelegate(item->id)->ShouldShowTooltip();
 }
 
 base::string16 ShelfView::GetTitleForView(const views::View* view) const {
   const ShelfItem* item = ShelfItemForView(view);
-  if (!item)
+  if (!item || !item_manager_->GetShelfItemDelegate(item->id))
     return base::string16();
   return item_manager_->GetShelfItemDelegate(item->id)->GetTitle();
 }
 
 gfx::Rect ShelfView::GetVisibleItemsBoundsInScreen() {
   gfx::Size preferred_size = GetPreferredSize();
   gfx::Point origin(GetMirroredXWithWidthInView(0, preferred_size.width()), 0);
   ConvertPointToScreen(this, &origin);
   return gfx::Rect(origin, preferred_size);
 }
@@ skipping 1331 matching lines @@
 
 int ShelfView::CalculateShelfDistance(const gfx::Point& coordinate) const {
   const gfx::Rect bounds = GetBoundsInScreen();
   int distance = shelf_->SelectValueForShelfAlignment(
       bounds.y() - coordinate.y(), coordinate.x() - bounds.right(),
       bounds.x() - coordinate.x());
   return distance > 0 ? distance : 0;
 }
 
 }  // namespace ash