Implement ui::ClipboardMus.

ui/views/mus/BUILD.gn

Index: ui/views/mus/BUILD.gn
diff --git a/ui/views/mus/BUILD.gn b/ui/views/mus/BUILD.gn
index abca967b4f81d0c96f9a45f02259fab75ede6704..5b75eddccb73ee2ad2c44eeeebcf5f8de1d2064f 100644
--- a/ui/views/mus/BUILD.gn
+++ b/ui/views/mus/BUILD.gn
@@ -15,6 +15,8 @@ component("mus") {
   sources = [
     "aura_init.cc",
     "aura_init.h",
+    "clipboard_mus.cc",
+    "clipboard_mus.h",
     "display_list.cc",
     "display_list.h",
     "input_method_mus.cc",
@@ -57,6 +59,7 @@ component("mus") {
     "//components/mus/public/cpp",
     "//components/mus/public/cpp/surfaces",
     "//components/mus/public/interfaces",
+    "//mojo/common",
     "//mojo/public/c/system:for_component",
     "//mojo/public/cpp/bindings",
     "//services/catalog/public/cpp",
@@ -243,6 +246,7 @@ test("views_mus_interactive_ui_tests") {
 
   sources = [
     "../widget/widget_interactive_uitest.cc",
+    "clipboard_unittest.cc",
     "interactive_ui_tests_mus.cc",
   ]
 
@@ -251,6 +255,8 @@ test("views_mus_interactive_ui_tests") {
     ":test_support",
     "//base",
     "//services/shell/background:main",  # Provides main().
+    "//testing/gmock",
+    "//testing/gtest",
     "//ui/aura",
     "//ui/base",
     "//ui/base/ime",