Provides a way to use bindings that doesn't require subclassing

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 da1055de535bb71445541320ab274be536bd5fe1..1fd430edf808fe501cd7075741cf29930e51593a 100644
--- a/mojo/public/cpp/bindings/interface_impl.h
+++ b/mojo/public/cpp/bindings/interface_impl.h
@@ -5,6 +5,7 @@
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_IMPL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_IMPL_H_
 
+#include "mojo/public/cpp/bindings/interface_binding.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/lib/interface_impl_internal.h"
 #include "mojo/public/cpp/environment/environment.h"
@@ -12,47 +13,60 @@
 
 namespace mojo {
 
+// Mojo provides two ways to bind an implementation of a particular interface to
+// a message pipe. The distinction lies in whether the binding logic is
+// inherited from a superclass (InterfaceImpl) or whether the binding is managed
+// separately from the class (InterfaceBinding). InterfaceImpl is generally
+// simpler to use at the cost of flexibility.
+
 // InterfaceImpl<..> is designed to be the base class of an interface
 // implementation. It may be bound to a pipe or a proxy, see BindToPipe and
 // BindToProxy.
+// See also InterfaceBinding.
 template <typename Interface>
-class InterfaceImpl : public internal::InterfaceImplBase<Interface> {
+class InterfaceImpl : public InterfaceBindingDelegate, public Interface {
  public:
   typedef typename Interface::Client Client;
   typedef Interface ImplementedInterface;
 
-  InterfaceImpl() : internal_state_(this) {}
-  virtual ~InterfaceImpl() {}
+  InterfaceImpl() : interface_binding_(nullptr) {}
+  virtual ~InterfaceImpl() { delete interface_binding_; }
 
   // Returns a proxy to the client interface. This is null upon construction,
   // and becomes non-null after OnClientConnected. NOTE: It remains non-null
   // until this instance is deleted.
-  Client* client() { return internal_state_.client(); }
+  Client* client() { return internal_state()->client(); }
 
   // Blocks the current thread for the first incoming method call, i.e., either
   // a call to a method or a client callback method. Returns |true| if a method
   // has been called, |false| in case of error. It must only be called on a
   // bound object.
   bool WaitForIncomingMethodCall() {
-    return internal_state_.WaitForIncomingMethodCall();
+    return internal_state()->WaitForIncomingMethodCall();
   }
 
-  // Called when the client has connected to this instance.
-  virtual void OnConnectionEstablished() {}
-
   // Called when the client is no longer connected to this instance. NOTE: The
   // client() method continues to return a non-null pointer after this method
   // is called. After this method is called, any method calls made on client()
   // will be silently ignored.
-  virtual void OnConnectionError() {}
+  void OnConnectionError() override {}
 
   // DO NOT USE. Exposed only for internal use and for testing.
   internal::InterfaceImplState<Interface>* internal_state() {
-    return &internal_state_;
+    return &interface_binding_->internal_state_;
+  }
+
+  // TODO(sky): move to private and friend functions that use.
+  void CreateInterfaceBinding() {
+    MOJO_DCHECK(!interface_binding_);
+    interface_binding_ = new InterfaceBinding<Interface>(this, this);
+    interface_binding_->set_owns_interface(false);
+    interface_binding_->set_delete_interface_on_error(true);
   }
 
  private:
-  internal::InterfaceImplState<Interface> internal_state_;
+  InterfaceBinding<Interface>* interface_binding_;
+
   MOJO_DISALLOW_COPY_AND_ASSIGN(InterfaceImpl);
 };
 
@@ -69,21 +83,25 @@ class InterfaceImpl : public internal::InterfaceImplBase<Interface> {
 // method will be called.
 //
 // Before returning, the instance's OnConnectionEstablished method is called.
-template <typename Impl>
+template <typename Impl,
+          typename Interface = typename Impl::ImplementedInterface>
 Impl* BindToPipe(
     Impl* instance,
     ScopedMessagePipeHandle handle,
     const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter()) {
+  instance->CreateInterfaceBinding();
   instance->internal_state()->Bind(handle.Pass(), true, waiter);
   return instance;
 }
 
 // Like BindToPipe but does not delete the instance after a channel error.
-template <typename Impl>
+template <typename Impl,
+          typename Interface = typename Impl::ImplementedInterface>
 Impl* WeakBindToPipe(
     Impl* instance,
     ScopedMessagePipeHandle handle,
     const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter()) {
+  instance->CreateInterfaceBinding();
   instance->internal_state()->Bind(handle.Pass(), false, waiter);
   return instance;
 }
@@ -104,6 +122,7 @@ Impl* BindToProxy(
     Impl* instance,
     InterfacePtr<Interface>* ptr,
     const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter()) {
+  instance->CreateInterfaceBinding();
   instance->internal_state()->BindProxy(ptr, true, waiter);
   return instance;
 }
@@ -114,6 +133,7 @@ Impl* WeakBindToProxy(
     Impl* instance,
     InterfacePtr<Interface>* ptr,
     const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter()) {
+  instance->CreateInterfaceBinding();
   instance->internal_state()->BindProxy(ptr, false, waiter);
   return instance;
 }