mus: Introduce AttachSurface to allow creating Surface prior to OnEmbed

components/mus/public/cpp/lib/window_surface.cc

Index: components/mus/public/cpp/lib/window_surface.cc
diff --git a/components/mus/public/cpp/lib/window_surface.cc b/components/mus/public/cpp/lib/window_surface.cc
index 83c4be011dda8a7549267aeaae1e63c8f4ed2e43..076243cadfdcb7a98f6777d795f9541ec4087dbe 100644
--- a/components/mus/public/cpp/lib/window_surface.cc
+++ b/components/mus/public/cpp/lib/window_surface.cc
@@ -9,11 +9,25 @@
 
 namespace mus {
 
+// static
+scoped_ptr<WindowSurface> WindowSurface::Create(
+    scoped_ptr<WindowSurfaceBinding>* surface_binding) {
+  mojom::SurfacePtr surface;
+  mojom::SurfaceClientPtr surface_client;
+  mojo::InterfaceRequest<mojom::SurfaceClient> surface_client_request =
+      GetProxy(&surface_client);
+
+  surface_binding->reset(
+      new WindowSurfaceBinding(GetProxy(&surface), surface_client.Pass()));
+  return make_scoped_ptr(new WindowSurface(surface.PassInterface(),
+                                           surface_client_request.Pass()));
+}
+
 WindowSurface::~WindowSurface() {}
 
 void WindowSurface::BindToThread() {
-  DCHECK(!bound_to_thread_);
-  bound_to_thread_ = true;
+  DCHECK(!thread_checker_);
+  thread_checker_.reset(new base::ThreadChecker());
   surface_.Bind(surface_info_.Pass());
   client_binding_.reset(
       new mojo::Binding<mojom::SurfaceClient>(this, client_request_.Pass()));
@@ -21,7 +35,8 @@ void WindowSurface::BindToThread() {
 
 void WindowSurface::SubmitCompositorFrame(mojom::CompositorFramePtr frame,
                                           const mojo::Closure& callback) {
-  DCHECK(bound_to_thread_);
+  DCHECK(thread_checker_);
+  DCHECK(thread_checker_->CalledOnValidThread());
   if (!surface_)
     return;
   surface_->SubmitCompositorFrame(frame.Pass(), callback);
@@ -32,14 +47,23 @@ WindowSurface::WindowSurface(
     mojo::InterfaceRequest<mojom::SurfaceClient> client_request)
     : client_(nullptr),
       surface_info_(surface_info.Pass()),
-      client_request_(client_request.Pass()),
-      bound_to_thread_(false) {}
+      client_request_(client_request.Pass()) {}
 
 void WindowSurface::ReturnResources(
     mojo::Array<mojom::ReturnedResourcePtr> resources) {
+  DCHECK(thread_checker_);
+  DCHECK(thread_checker_->CalledOnValidThread());
   if (!client_)
     return;
   client_->OnResourcesReturned(this, resources.Pass());
 }
 
+WindowSurfaceBinding::~WindowSurfaceBinding() {}
+
+WindowSurfaceBinding::WindowSurfaceBinding(
+    mojo::InterfaceRequest<mojom::Surface> surface_request,
+    mojom::SurfaceClientPtr surface_client)
+    : surface_request_(surface_request.Pass()),
+      surface_client_(surface_client.Pass()) {}
+
 }  // namespace mus