Allow constructing a StrongBinding with an InterfacePtr*

mojo/public/cpp/bindings/strong_binding.h

Index: mojo/public/cpp/bindings/strong_binding.h
diff --git a/mojo/public/cpp/bindings/strong_binding.h b/mojo/public/cpp/bindings/strong_binding.h
index 73966ff8254316a6fbdcff3e40e775d8ef49fccb..106b282e46f755485e5d4626596a4f64c6b7bf01 100644
--- a/mojo/public/cpp/bindings/strong_binding.h
+++ b/mojo/public/cpp/bindings/strong_binding.h
@@ -51,6 +51,14 @@ class StrongBinding : public ErrorHandler {
 
   StrongBinding(
       Interface* impl,
+      InterfacePtr<Interface>* ptr,
+      const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter())
+      : StrongBinding(impl) {
+    binding_.Bind(ptr, waiter);
+  }
+
+  StrongBinding(
+      Interface* impl,
       InterfaceRequest<Interface> request,
       const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter())
       : StrongBinding(impl) {