Adds ScopedHandleBase::From

mojo/public/cpp/bindings/interface.h

Index: mojo/public/cpp/bindings/interface.h
diff --git a/mojo/public/cpp/bindings/interface.h b/mojo/public/cpp/bindings/interface.h
index bba8fef89fc685b0f6b46841363450f5cb321009..ff6bf36a4267e7669380bb2a97af1ef433fcafbc 100644
--- a/mojo/public/cpp/bindings/interface.h
+++ b/mojo/public/cpp/bindings/interface.h
@@ -63,6 +63,16 @@ struct Interface<mojo::NoInterface> {
   typedef ScopedMessagePipeHandle ScopedHandle;
 };
 
+// Use to convert from a ScopedMessagePipeHandle to an scoped interface
+// handle. For example,
+// ConvertToInterface<OmniboxPage>(message_pip_handle.Pass()),

[vtl, 2014/04/03 14:58:30]

drive-by nit: message_pip -> message_pipe

+// where OmniboxPage names an interface in a mojom file.
+template <typename S>
+typename Interface<S>::ScopedHandle ConvertToInterface(
+    ScopedMessagePipeHandle message_pipe_handle) {
+  return Interface<S>::ScopedHandle(
+      Interface<S>::Handle(message_pipe_handle.release().value()));
+}
 
 // InterfacePipe<S,P> is used to construct a MessagePipe with typed interfaces
 // on either end.