First cut at "content handling" support in Mojo.

mojo/shell/network_service_loader.cc

Index: mojo/shell/network_service_loader.cc
diff --git a/mojo/shell/network_service_loader.cc b/mojo/shell/network_service_loader.cc
index 9f8f87f0b7f62ada1c6a8f836e061f58797005f7..e04b434bc85e69505b16771f9b4f71e64b26804f 100644
--- a/mojo/shell/network_service_loader.cc
+++ b/mojo/shell/network_service_loader.cc
@@ -32,7 +32,12 @@ NetworkServiceLoader::~NetworkServiceLoader() {
 void NetworkServiceLoader::LoadService(
     ServiceManager* manager,
     const GURL& url,
-    ScopedMessagePipeHandle shell_handle) {
+    scoped_refptr<LoadServiceCallbacks> callbacks) {
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid()) {
+    return;
+  }
+
   uintptr_t key = reinterpret_cast<uintptr_t>(manager);
   if (apps_.find(key) == apps_.end()) {
     scoped_ptr<ApplicationImpl> app(