Create separate BUILD.gn for //apps/ui/views

apps/ui/views/BUILD.gn

+# Copyright 2017 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.
+
+import("//build/config/ui.gni")
+import("//extensions/features/features.gni")
+
+assert(enable_extensions)
+
+source_set("views") {
+  sources = [
+    "app_window_frame_view.cc",
+    "app_window_frame_view.h",
+  ]
+
+  deps = [
+    "//cc/paint",
+    "//chrome/app/theme:theme_resources",
+    "//extensions/browser/app_window",
+    "//extensions/common",
+    "//skia",
+    "//ui/gfx",
+    "//ui/strings",
+    "//ui/views",
+  ]
+}