ws: Enable the Window Service clipboard backend for mojo apps

Have ws2::WindowService own a ClipboardImpl, like ws::Service.
Enables copy/paste within the ksv app, but not to/from ash/chrome.
(run ksv app via --keyboard-shortcut-viewer-app, press Ctrl+Alt+/).

TODO: Support copy-paste between mojo apps and Chrome/Ash.

Bug: 839591
Change-Id: I02b05cb9f830b0053dc0f1ad9e8e702505ad10a4
Reviewed-on: https://chromium-review.googlesource.com/1073572
Commit-Queue: Michael Wasserman <msw@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561923}

services/ui/ws2/BUILD.gn

@@ -54,6 +54,7 @@ component("lib") {
     "//components/discardable_memory/public/interfaces",
     "//components/viz/host",
     "//services/service_manager/public/cpp",
+    "//services/ui/clipboard:lib",
     "//services/ui/common:mus_common",
     "//services/ui/ime:lib",
     "//services/ui/input_devices",

services/ui/ws2/window_service.cc

@@ -101,8 +101,9 @@ void WindowService::OnBindInterface(
 }
 
 void WindowService::BindClipboardRequest(mojom::ClipboardRequest request) {
-  // TODO: https://crbug.com/839591.
-  NOTIMPLEMENTED();
+  if (!clipboard_)
+    clipboard_ = std::make_unique<clipboard::ClipboardImpl>();
+  clipboard_->AddBinding(std::move(request));
 }
 
 void WindowService::BindScreenProviderRequest(

services/ui/ws2/window_service.h

@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "services/service_manager/public/cpp/binder_registry.h"
 #include "services/service_manager/public/cpp/service.h"
+#include "services/ui/clipboard/clipboard_impl.h"
 #include "services/ui/ime/ime_driver_bridge.h"
 #include "services/ui/ime/ime_registrar_impl.h"
 #include "services/ui/input_devices/input_device_server.h"
@@ -28,6 +29,10 @@ class FocusClient;
 }
 }
 
+namespace clipboard {
+class ClipboardImpl;
+}
+
 namespace gfx {
 class Insets;
 }
@@ -112,6 +117,8 @@ class COMPONENT_EXPORT(WINDOW_SERVICE) WindowService
   // Provides info to InputDeviceClient users, via InputDeviceManager.
   ui::InputDeviceServer input_device_server_;
 
+  std::unique_ptr<clipboard::ClipboardImpl> clipboard_;
+
   // Id for the next WindowServiceClient.
   ClientSpecificId next_client_id_ = kWindowServerClientId + 1;