Add a card background to the app list search result groups.

ui/app_list/views/search_result_page_view.cc

Index: ui/app_list/views/search_result_page_view.cc
diff --git a/ui/app_list/views/search_result_page_view.cc b/ui/app_list/views/search_result_page_view.cc
index c925f73852fafc5465e8934f0c5840533e90ac71..68e78e3259b5c910f79e4b8a88a0101b5a04e9ae 100644
--- a/ui/app_list/views/search_result_page_view.cc
+++ b/ui/app_list/views/search_result_page_view.cc
@@ -9,13 +9,38 @@
 #include "ui/app_list/views/app_list_main_view.h"
 #include "ui/app_list/views/search_result_list_view.h"
 #include "ui/app_list/views/search_result_tile_item_list_view.h"
+#include "ui/views/background.h"
 #include "ui/views/layout/box_layout.h"
+#include "ui/views/layout/fill_layout.h"
+#include "ui/views/shadow_border.h"
 
 namespace app_list {
 
 namespace {
 
 const int kGroupSpacing = 20;
+const int kTopPadding = 5;
+
+// A container view that ensures the card background and the shadow are painted
+// in the correct order.
+class SearchCardView : public views::View {
+ public:
+  SearchCardView(views::View* content_view) {
+    SetBorder(make_scoped_ptr(new views::ShadowBorder(
+        kCardShadowBlur, kCardShadowColor, kCardShadowYOffset, 0)));
+    SetLayoutManager(new views::FillLayout());
+    content_view->set_background(
+        views::Background::CreateSolidBackground(kCardBackgroundColor));
+    AddChildView(content_view);
+  }
+
+  ~SearchCardView() override {}
+
+  void ChildPreferredSizeChanged(views::View* child) override {
+    Layout();
+    PreferredSizeChanged();
+  }
+};
 
 }  // namespace
 
@@ -25,14 +50,14 @@ SearchResultPageView::SearchResultPageView(AppListMainView* app_list_main_view,
           new SearchResultListView(app_list_main_view, view_delegate)),
       tiles_view_(new SearchResultTileItemListView()) {
   SetLayoutManager(new views::BoxLayout(views::BoxLayout::kVertical,
-                                        kExperimentalWindowPadding, 0,
+                                        kExperimentalWindowPadding, kTopPadding,
                                         kGroupSpacing));
 
   // The view containing the search results.
-  AddChildView(results_view_);
+  AddChildView(new SearchCardView(results_view_));
 
   // The view containing the start page tiles.
-  AddChildView(tiles_view_);
+  AddChildView(new SearchCardView(tiles_view_));
 
   AppListModel::SearchResults* model = view_delegate->GetModel()->results();
   results_view_->SetResults(model);