Use a background for the main search box in the experimental app list.

ui/app_list/views/app_list_background.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 "ui/app_list/views/app_list_background.h"
 
 #include "base/command_line.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkPath.h"
 #include "ui/app_list/app_list_constants.h"
@@ skipping 36 matching lines @@
   // Contents corner radius is 1px smaller than border corner radius.
   SkScalar radius = SkIntToScalar(corner_radius_ - 1);
   path.addRoundRect(gfx::RectToSkRect(bounds), radius, radius);
   canvas->ClipPath(path, false);
 
   SkPaint paint;
   paint.setStyle(SkPaint::kFill_Style);
 
   int contents_top = bounds.y();
   views::View* search_box_view = main_view_->search_box_view();
-  if (main_view_->visible() && search_box_view->visible()) {
+  if (main_view_->visible() && search_box_view->visible() &&
+      !app_list::switches::IsExperimentalAppListEnabled()) {
     const gfx::Rect search_box_view_bounds =
         search_box_view->ConvertRectToWidget(search_box_view->GetLocalBounds());
     gfx::Rect search_box_rect(bounds.x(),
                               bounds.y(),
                               bounds.width(),
                               search_box_view_bounds.bottom() - bounds.y());
 
     paint.setColor(kSearchBoxBackground);
     canvas->DrawRect(search_box_rect, paint);
 
@@ skipping 31 matching lines @@
                                        bounds.bottom() - contents_switcher_top);
       paint.setColor(kContentsSwitcherBackgroundColor);
       canvas->DrawRect(contents_switcher_rect, paint);
     }
   }
 
   canvas->Restore();
 }
 
 }  // namespace app_list