Move content's shell connections to the IO thread

services/shell/public/cpp/interface_registry.h

Index: services/shell/public/cpp/interface_registry.h
diff --git a/services/shell/public/cpp/interface_registry.h b/services/shell/public/cpp/interface_registry.h
index 98f85550fab9959bc538ecc86782f0fe86b82ceb..0005b4510ed6061d8b5fd502c3f01575ed69d579 100644
--- a/services/shell/public/cpp/interface_registry.h
+++ b/services/shell/public/cpp/interface_registry.h
@@ -7,6 +7,7 @@
 
 #include <memory>
 
+#include "base/callback.h"
 #include "base/memory/ptr_util.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "services/shell/public/cpp/lib/callback_binder.h"
@@ -40,6 +41,9 @@ class InterfaceBinder;
 //
 class InterfaceRegistry : public mojom::InterfaceProvider {
  public:
+  using Binder = base::Callback<void(const mojo::String&,
+                                     mojo::ScopedMessagePipeHandle)>;
+
   class TestApi {
    public:
     explicit TestApi(InterfaceRegistry* registry) : registry_(registry) {}
@@ -64,6 +68,10 @@ class InterfaceRegistry : public mojom::InterfaceProvider {
   explicit InterfaceRegistry(Connection* connection);
   ~InterfaceRegistry() override;
 
+  // Sets a default handler for incoming interface requests which are allowed by
+  // capability filters but have no registered handler in this registry.
+  void set_default_binder(const Binder& binder) { default_binder_ = binder; }
+
   void Bind(mojom::InterfaceProviderRequest local_interfaces_request);
 
   base::WeakPtr<InterfaceRegistry> GetWeakPtr();
@@ -132,6 +140,8 @@ class InterfaceRegistry : public mojom::InterfaceProvider {
 
   NameToInterfaceBinderMap name_to_binder_;
 
+  Binder default_binder_;
+
   base::WeakPtrFactory<InterfaceRegistry> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(InterfaceRegistry);