Changed previews component to be a layered component.

components/previews/core/BUILD.gn

Index: components/previews/core/BUILD.gn
diff --git a/components/previews/BUILD.gn b/components/previews/core/BUILD.gn
similarity index 95%
rename from components/previews/BUILD.gn
rename to components/previews/core/BUILD.gn
index 26efc4f370f65fc26e1e252cbd99d7b718014557..e59a40ba50e6314694838c687b1a3036305d159f 100644
--- a/components/previews/BUILD.gn
+++ b/components/previews/core/BUILD.gn
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-static_library("previews") {
+static_library("core") {
   sources = [
     "previews_data_savings.cc",
     "previews_data_savings.h",
@@ -31,7 +31,7 @@ source_set("unit_tests") {
   ]
 
   deps = [
-    ":previews",
+    ":core",
     "//base",
     "//base/test:test_support",
     "//components/data_reduction_proxy/core/common",