Introduce a layering in the invalidation component as public and impl

components/invalidation/public/BUILD.gn

Index: components/invalidation/public/BUILD.gn
diff --git a/components/invalidation/public/BUILD.gn b/components/invalidation/public/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..8cee3149c32ab79faf1f37b7af71dcecd038ef55
--- /dev/null
+++ b/components/invalidation/public/BUILD.gn
@@ -0,0 +1,32 @@
+# Copyright 2015 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("public") {
+  sources = [
+    "ack_handle.cc",
+    "ack_handle.h",
+    "ack_handler.cc",
+    "ack_handler.h",
+    "invalidation.cc",
+    "invalidation.h",
+    "invalidation_export.h",
+    "invalidation_handler.cc",
+    "invalidation_handler.h",
+    "invalidation_service.h",
+    "invalidation_util.cc",
+    "invalidation_util.h",
+    "invalidator_state.cc",
+    "invalidator_state.h",
+    "object_id_invalidation_map.cc",
+    "object_id_invalidation_map.h",
+    "single_object_invalidation_set.cc",
+    "single_object_invalidation_set.h",
+  ]
+  public_deps = [
+    "//third_party/cacheinvalidation",
+  ]
+  deps = [
+    "//base",
+  ]
+}