services/ui: Create a proper component for the client-lib.

services/ui/public/cpp/window_tree_client.h

Index: services/ui/public/cpp/window_tree_client.h
diff --git a/services/ui/public/cpp/window_tree_client.h b/services/ui/public/cpp/window_tree_client.h
index 5f11f731b219761bb7f976d573e59a5f24b07486..3e5217ad90bbf099bf17caf29998273b56b1fa43 100644
--- a/services/ui/public/cpp/window_tree_client.h
+++ b/services/ui/public/cpp/window_tree_client.h
@@ -20,6 +20,7 @@
 #include "mojo/public/cpp/bindings/associated_binding.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "services/ui/common/types.h"
+#include "services/ui/public/cpp/ui_export.h"
 #include "services/ui/public/cpp/window.h"
 #include "services/ui/public/cpp/window_manager_delegate.h"
 #include "services/ui/public/interfaces/window_tree.mojom.h"
@@ -58,9 +59,10 @@ enum class ChangeType;
 // When WindowTreeClient is deleted all windows are deleted (and observers
 // notified). This is followed by calling
 // WindowTreeClientDelegate::OnDidDestroyClient().
-class WindowTreeClient : public mojom::WindowTreeClient,
-                         public mojom::WindowManager,
-                         public WindowManagerClient {
+class UI_EXPORT WindowTreeClient
+    : NON_EXPORTED_BASE(public mojom::WindowTreeClient),
+      NON_EXPORTED_BASE(public mojom::WindowManager),
+      public WindowManagerClient {
  public:
   WindowTreeClient(WindowTreeClientDelegate* delegate,
                    WindowManagerDelegate* window_manager_delegate,