Use CapabilityFilter to restrict what HTMLViewers can connect to.

mojo/application/public/cpp/application_impl.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_APPLICATION_PUBLIC_CPP_APPLICATION_IMPL_H_
 #define MOJO_APPLICATION_PUBLIC_CPP_APPLICATION_IMPL_H_
 
 #include <vector>
 
 #include "base/memory/scoped_vector.h"
@@ skipping 62 matching lines @@
   // the ApplicationImpl is destroyed.
   Shell* shell() const { return shell_.get(); }
 
   const std::string& url() const { return url_; }
 
   AppLifetimeHelper* app_lifetime_helper() { return &app_lifetime_helper_; }
 
   // Requests a new connection to an application. Returns a pointer to the
   // connection if the connection is permitted by this application's delegate,
   // or nullptr otherwise. Caller takes ownership.
-  // TODO(beng): consider replacing default value in a separate CL per style
-  //             guide.
-  scoped_ptr<ApplicationConnection> ConnectToApplication(
+  scoped_ptr<ApplicationConnection> ConnectToApplication(URLRequestPtr request);
+  scoped_ptr<ApplicationConnection> ConnectToApplicationWithCapabilityFilter(
       URLRequestPtr request,
-      CapabilityFilterPtr filter = nullptr);
+      CapabilityFilterPtr filter);
 
   // Connect to application identified by |request->url| and connect to the
   // service implementation of the interface identified by |Interface|.
   template <typename Interface>
   void ConnectToService(mojo::URLRequestPtr request,
                         InterfacePtr<Interface>* ptr) {
     scoped_ptr<ApplicationConnection> connection =
         ConnectToApplication(request.Pass());
     if (!connection.get())
       return;
@@ skipping 42 matching lines @@
   AppLifetimeHelper app_lifetime_helper_;
   bool quit_requested_;
   base::WeakPtrFactory<ApplicationImpl> weak_factory_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(ApplicationImpl);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_APPLICATION_PUBLIC_CPP_APPLICATION_IMPL_H_