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

mojo/public/cpp/bindings/lib/interface_impl_internal.h

Index: mojo/public/cpp/bindings/lib/interface_impl_internal.h
diff --git a/mojo/public/cpp/bindings/lib/interface_impl_internal.h b/mojo/public/cpp/bindings/lib/interface_impl_internal.h
index 492b1822496749d6d68dea24f71fc866d5193a11..c9e3315d5fcea305eee3841c72ba18370e7e05b5 100644
--- a/mojo/public/cpp/bindings/lib/interface_impl_internal.h
+++ b/mojo/public/cpp/bindings/lib/interface_impl_internal.h
@@ -6,6 +6,7 @@
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_IMPL_INTERNAL_H_
 
 #include "mojo/public/cpp/bindings/error_handler.h"
+#include "mojo/public/cpp/bindings/interface_binding_delegate.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/lib/filter_chain.h"
 #include "mojo/public/cpp/bindings/lib/message_header_validator.h"
@@ -14,38 +15,27 @@
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
-namespace internal {
 
-template <typename Interface>
-class InterfaceImplBase : public Interface {
- public:
-  virtual ~InterfaceImplBase() {}
-  virtual void OnConnectionEstablished() = 0;
-  virtual void OnConnectionError() = 0;
-};
+class InterfaceBindingDelegate;
+
+namespace internal {
 
 template <typename Interface>
 class InterfaceImplState : public ErrorHandler {
  public:
   typedef typename Interface::Client Client;
 
-  explicit InterfaceImplState(InterfaceImplBase<Interface>* instance)
-      : router_(nullptr),
+  explicit InterfaceImplState(Interface* instance,
+                              InterfaceBindingDelegate* delegate)
+      : delegate_(delegate),
+        router_(nullptr),
         proxy_(nullptr),
-        instance_bound_to_pipe_(false)
-#ifndef NDEBUG
-        ,
-        deleting_instance_due_to_error_(false)
-#endif
-  {
+        instance_bound_to_pipe_(false) {
     MOJO_DCHECK(instance);
     stub_.set_sink(instance);
   }
 
   virtual ~InterfaceImplState() {
-#ifndef NDEBUG
-    MOJO_DCHECK(!instance_bound_to_pipe_ || deleting_instance_due_to_error_);
-#endif
     delete proxy_;
     if (router_) {
       router_->set_error_handler(nullptr);
@@ -80,7 +70,8 @@ class InterfaceImplState : public ErrorHandler {
 
     instance_bound_to_pipe_ = instance_bound_to_pipe;
 
-    instance()->OnConnectionEstablished();
+    if (delegate_)
+      delegate_->OnConnectionEstablished();
   }
 
   bool WaitForIncomingMethodCall() {
@@ -90,34 +81,18 @@ class InterfaceImplState : public ErrorHandler {
 
   Router* router() { return router_; }
   Client* client() { return proxy_; }
+  Interface* instance() { return stub_.sink(); }
 
- private:
-  InterfaceImplBase<Interface>* instance() {
-    return static_cast<InterfaceImplBase<Interface>*>(stub_.sink());
-  }
+  bool instance_bound_to_pipe() const { return instance_bound_to_pipe_; }
 
-  virtual void OnConnectionError() override {
-    // If the the instance is not bound to the pipe, the instance might choose
-    // to delete itself in the OnConnectionError handler, which would in turn
-    // delete this.  Save the error behavior before invoking the error handler
-    // so we can correctly decide what to do.
-    bool bound = instance_bound_to_pipe_;
-    instance()->OnConnectionError();
-    if (!bound)
-      return;
-#ifndef NDEBUG
-    deleting_instance_due_to_error_ = true;
-#endif
-    delete instance();
-  }
+ private:
+  virtual void OnConnectionError() override { delegate_->OnConnectionError(); }
 
+  InterfaceBindingDelegate* delegate_;
   Router* router_;
   typename Client::Proxy_* proxy_;
   typename Interface::Stub_ stub_;
   bool instance_bound_to_pipe_;
-#ifndef NDEBUG
-  bool deleting_instance_due_to_error_;
-#endif
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(InterfaceImplState);
 };