De-Client Surface interface

mojo.Surface's client had two methods:

*) SetIdNamespace replaced by mojo.Surface.GetIdNamespace which returns
the id namespace via a callback.

*) ReturnResources split into a ResourceReturner interface which can be
(optionally) set on the mojo.Surface via
mojo.Surface.SetResourceReturner

Also beefed up the comments a bit.

BUG=451319
R=sky@chromium.org

Review URL: https://codereview.chromium.org/871373015

compositor/surface_holder.cc

@@ -17,12 +17,20 @@ SurfaceHolder::Client::~Client() {
 }
 
 SurfaceHolder::SurfaceHolder(Client* client, mojo::Shell* shell)
-    : client_(client), id_namespace_(0u), local_id_(0u), weak_factory_(this) {
+    : client_(client),
+      id_namespace_(0u),
+      local_id_(0u),
+      returner_binding_(this),
+      weak_factory_(this) {
   mojo::ServiceProviderPtr service_provider;
   shell->ConnectToApplication("mojo:surfaces_service",
                               mojo::GetProxy(&service_provider), nullptr);
   mojo::ConnectToService(service_provider.get(), &surface_);
-  surface_.set_client(this);
+  surface_->GetIdNamespace(
+      base::Bind(&SurfaceHolder::SetIdNamespace, base::Unretained(this)));
+  mojo::ResourceReturnerPtr returner_ptr;
+  returner_binding_.Bind(GetProxy(&returner_ptr));
+  surface_->SetResourceReturner(returner_ptr.Pass());
 }
 
 SurfaceHolder::~SurfaceHolder() {
@@ -65,9 +73,6 @@ void SurfaceHolder::SetIdNamespace(uint32_t id_namespace) {
 
 void SurfaceHolder::ReturnResources(
     mojo::Array<mojo::ReturnedResourcePtr> resources) {
-  // TODO(abarth): The surface service shouldn't spam us with empty calls.
-  if (!resources.size())
-    return;
   client_->ReturnResources(resources.Pass());
 }
 

compositor/surface_holder.h

@@ -19,7 +19,7 @@ class Shell;
 namespace sky {
 class SurfaceAllocator;
 
-class SurfaceHolder : public mojo::SurfaceClient {
+class SurfaceHolder : public mojo::ResourceReturner {
  public:
   class Client {
    public:
@@ -38,11 +38,11 @@ class SurfaceHolder : public mojo::SurfaceClient {
   void SubmitFrame(mojo::FramePtr frame, const base::Closure& callback);
 
  private:
-  // mojo::SurfaceClient
-  void SetIdNamespace(uint32_t id_namespace) override;
+  // mojo::ResourceReturner
   void ReturnResources(
       mojo::Array<mojo::ReturnedResourcePtr> resources) override;
 
+  void SetIdNamespace(uint32_t id_namespace);
   void SetQualifiedId();
 
   Client* client_;
@@ -50,6 +50,7 @@ class SurfaceHolder : public mojo::SurfaceClient {
   uint32_t id_namespace_;
   uint32_t local_id_;
   mojo::SurfacePtr surface_;
+  mojo::Binding<mojo::ResourceReturner> returner_binding_;
 
   base::WeakPtrFactory<SurfaceHolder> weak_factory_;