Create a RegisterViewAssociate method in ViewManager

services/ui/view_manager/BUILD.gn

 # 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.
 
 import("//mojo/public/mojo_application.gni")
 import("//testing/test.gni")
 
-mojo_native_application("view_manager") {
-  output_name = "view_manager_service"
-
+source_set("common") {
   sources = [
-    "main.cc",
     "view_associate_table.cc",
     "view_associate_table.h",
     "view_container_state.cc",
     "view_container_state.h",
     "view_impl.cc",
     "view_impl.h",
     "view_manager_app.cc",
     "view_manager_app.h",
     "view_manager_impl.cc",
     "view_manager_impl.h",
     "view_registry.cc",
     "view_registry.h",
     "view_state.cc",
     "view_state.h",
     "view_stub.cc",
     "view_stub.h",
     "view_tree_impl.cc",
     "view_tree_impl.h",
     "view_tree_state.cc",
     "view_tree_state.h",
   ]
 
-  deps = [
+  public_deps = [
     "//base",
     "//mojo/application",
     "//mojo/common",
     "//mojo/common:tracing_impl",
     "//mojo/converters/geometry",
-    "//mojo/environment:chromium",
     "//mojo/public/cpp/bindings:bindings",
     "//mojo/services/geometry/cpp",
     "//mojo/services/gfx/composition/cpp",
     "//mojo/services/gfx/composition/interfaces",
     "//mojo/services/ui/views/cpp",
     "//mojo/services/ui/views/interfaces",
   ]
 }
+
+mojo_native_application("view_manager") {
+  output_name = "view_manager_service"
+
+  sources = [
+    "main.cc",
+  ]
+
+  deps = [
+    ":common",
+    "//mojo/environment:chromium",
+  ]
+}
+
+mojo_native_application("view_manager_apptests") {
+  output_name = "view_manager_apptests"
+
+  testonly = true
+
+  sources = [
+    "tests/mock_view_associate.cc",
+    "tests/mock_view_associate.h",
+    "tests/view_associate_table_test.cc",
+    "tests/view_manager_test.cc",
+    "tests/view_manager_test_base.cc",
+    "tests/view_manager_test_base.h",
+  ]
+
+  deps = [
+    ":common",
+    "//base",
+    "//mojo/application:test_support",
+    "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/bindings:bindings",
+    "//mojo/ui/associates:mocks",
+  ]
+}