Changed previews component to be a layered component.

components/previews/BUILD.gn

Index: components/previews/BUILD.gn
diff --git a/components/previews/BUILD.gn b/components/previews/BUILD.gn
deleted file mode 100644
index 26efc4f370f65fc26e1e252cbd99d7b718014557..0000000000000000000000000000000000000000
--- a/components/previews/BUILD.gn
+++ /dev/null
@@ -1,41 +0,0 @@
-# Copyright 2016 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.
-
-static_library("previews") {
-  sources = [
-    "previews_data_savings.cc",
-    "previews_data_savings.h",
-    "previews_experiments.cc",
-    "previews_experiments.h",
-    "previews_io_data.cc",
-    "previews_io_data.h",
-    "previews_ui_service.cc",
-    "previews_ui_service.h",
-  ]
-
-  deps = [
-    "//base",
-    "//components/data_reduction_proxy/core/common",
-    "//components/variations",
-  ]
-}
-
-source_set("unit_tests") {
-  testonly = true
-  sources = [
-    "previews_data_savings_unittest.cc",
-    "previews_experiments_unittest.cc",
-    "previews_io_data_unittest.cc",
-    "previews_ui_service_unittest.cc",
-  ]
-
-  deps = [
-    ":previews",
-    "//base",
-    "//base/test:test_support",
-    "//components/data_reduction_proxy/core/common",
-    "//components/variations",
-    "//testing/gtest",
-  ]
-}