Add SetClient method implementation to InterfaceImpl.

mojo/public/cpp/bindings/interface_impl.h

Index: mojo/public/cpp/bindings/interface_impl.h
diff --git a/mojo/public/cpp/bindings/interface_impl.h b/mojo/public/cpp/bindings/interface_impl.h
index ec6bc9160e7701dcf4f45ef73c3d992fcb2d1bf9..a9d0947757d728bb773efe0538952ec1556a7151 100644
--- a/mojo/public/cpp/bindings/interface_impl.h
+++ b/mojo/public/cpp/bindings/interface_impl.h
@@ -20,12 +20,20 @@ namespace mojo {
 template <typename Interface>
 class InterfaceImpl : public WithErrorHandler<Interface> {
  public:
+  typedef typename Interface::Client Client;
+
   InterfaceImpl() : internal_state_(this) {}
   virtual ~InterfaceImpl() {}
 
   // Subclasses must handle connection errors.
   virtual void OnConnectionError() = 0;
 
+  // We override SetClient here so subclasses don't each have to.
+  virtual void SetClient(Client* client) MOJO_OVERRIDE {
+    internal_state_.set_client(client);
+  }
+  Client* client() { return internal_state_.client(); }
+
   // DO NOT USE. Exposed only for internal use and for testing.
   internal::InterfaceImplState<Interface>* internal_state() {
     return &internal_state_;