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

ui/app_list/app_list_constants.cc

Index: ui/app_list/app_list_constants.cc
diff --git a/ui/app_list/app_list_constants.cc b/ui/app_list/app_list_constants.cc
index 5997aa248b1bd18fe87509e2a7066aeb1c326984..bb1ae6efa976858ef83b7e2c973bd2782574086f 100644
--- a/ui/app_list/app_list_constants.cc
+++ b/ui/app_list/app_list_constants.cc
@@ -50,6 +50,9 @@ const float kFolderBubbleRadius = 22;
 const float kFolderShadowRadius = 22.5;
 const float kFolderShadowOffsetY = 1;
 
+const SkColor kCardShadowColor = SkColorSetARGB(0x25, 0, 0, 0);
+const SkColor kCardBackgroundColor = SK_ColorWHITE;
+
 // Duration in milliseconds for page transition.
 const int kPageTransitionDurationInMs = 180;