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 86c63388fc5340e1e767a11a7cb699beea6c467f..0d30a8238710d3938b994f051cb61e4e5a0d66ef 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",
@@ -59,6 +61,7 @@ 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",
@@ -244,6 +247,7 @@ test("views_mus_interactive_ui_tests") {
 
   sources = [
     "../widget/widget_interactive_uitest.cc",
+    "clipboard_unittest.cc",
     "interactive_ui_tests_mus.cc",
   ]
 
@@ -252,6 +256,8 @@ 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",