Set enable_app_list=1 now only on ChromeOS.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 7903e89d45f5301890429048a1ca8c1a89befab6..ad3070b1374a864b87eb9a4eae8b940d188ab32b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -267,22 +267,12 @@ group("both_gn_and_gyp") {
     deps += [ "//ui/views:views_unittests" ]
   }
 
-  if (enable_app_list) {
-    deps += [ "//ui/app_list:app_list_unittests" ]
-  }
-
-  if (enable_app_list && use_aura) {
-    deps += [
-      # TODO(tapted): Move this into enable_app_list when enable_app_list is not
-      # true on Mac.
-      "//ui/app_list/presenter:app_list_presenter_unittests",
-    ]
-  }
-
   if (use_aura) {
     deps += [
       "//ash:ash_shell_with_content",
       "//ash:ash_unittests",
+      "//ui/app_list:app_list_unittests",
+      "//ui/app_list/presenter:app_list_presenter_unittests",
       "//ui/aura:aura_unittests",
       "//ui/aura:demo",
       "//ui/wm:wm_unittests",