mojo: Make InterfacePtr<> testable in if() statements without .get().

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_INTERNAL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_INTERNAL_H_
 
 #include <assert.h>
 
 #include "mojo/public/cpp/bindings/lib/filter_chain.h"
@@ skipping 50 matching lines @@
   }
 
   ScopedMessagePipeHandle PassMessagePipe() {
     if (router_)
       return router_->PassMessagePipe();
 
     waiter_ = NULL;
     return handle_.Pass();
   }
 
+  bool is_bound() const {
+    return handle_.is_valid() || router_;
+  }
+
   void set_client(typename Interface::Client* client) {
     ConfigureProxyIfNecessary();
 
     assert(proxy_);
     proxy_->stub.set_sink(client);
   }
 
   bool encountered_error() const {
     return router_ ? router_->encountered_error() : false;
   }
@@ skipping 56 matching lines @@
   ScopedMessagePipeHandle handle_;
   const MojoAsyncWaiter* waiter_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(InterfacePtrState);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_INTERNAL_H_