Enable InputDeviceServer/InputDeviceClient in mash.

chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h

Index: chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
diff --git a/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h b/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
index 6cd1b8ba522623a65cbade5eca361da5a3a6d2a5..09b16c0e908cf30157737c2be3915dc4b1961e7a 100644
--- a/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
+++ b/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
@@ -10,6 +10,10 @@
 #include "base/macros.h"
 #include "chrome/browser/chrome_browser_main_extra_parts.h"
 
+namespace mus {
+class InputDeviceClient;
+}
+
 namespace views {
 class ViewsDelegate;
 class WindowManagerConnection;
@@ -39,6 +43,9 @@ class ChromeBrowserMainExtraPartsViews : public ChromeBrowserMainExtraParts {
 #endif
 #if defined(USE_AURA) && defined(MOJO_SHELL_CLIENT)
   std::unique_ptr<views::WindowManagerConnection> window_manager_connection_;
+
+  // Subscribes to updates about input-devices.
+  std::unique_ptr<mus::InputDeviceClient> input_device_client_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsViews);