Impl mus::mojom::GpuService to enable using Chrome IPC version gpu CmdBuf in mus

components/mus/public/cpp/window_tree_delegate.h

Index: components/mus/public/cpp/window_tree_delegate.h
diff --git a/components/mus/public/cpp/window_tree_delegate.h b/components/mus/public/cpp/window_tree_delegate.h
index 953bcbae43ff9c4cae8776ddb90afcca85e62e0e..92e9c0da9fa749137708fda91325fbadec2c54a4 100644
--- a/components/mus/public/cpp/window_tree_delegate.h
+++ b/components/mus/public/cpp/window_tree_delegate.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "components/mus/public/cpp/mus_public_export.h"
 #include "components/mus/public/interfaces/window_tree.mojom.h"
 #include "services/shell/public/interfaces/interface_provider.mojom.h"
 
@@ -32,7 +33,7 @@ class WindowTreeConnection;
 // When the WindowTreeConnection is deleted all windows are deleted (and
 // observers notified). This is followed by notifying the delegate by way of
 // OnConnectionLost().
-class WindowTreeDelegate {
+class MUS_PUBLIC_EXPORT WindowTreeDelegate {
  public:
   // Called when the application implementing this interface is embedded at
   // |root|.