Make TracingImpl take a Shell* and args, instead of an ApplicationImpl*.

services/dart/dart_tracing.cc

Index: services/dart/dart_tracing.cc
diff --git a/services/dart/dart_tracing.cc b/services/dart/dart_tracing.cc
index 45104c60c7f540639e324d89fa18fc789612d5ec..bf5b9a7b3bdb166f281f72255bc4834d381611ef 100644
--- a/services/dart/dart_tracing.cc
+++ b/services/dart/dart_tracing.cc
@@ -133,9 +133,9 @@ DartTracingImpl::DartTracingImpl() {
 DartTracingImpl::~DartTracingImpl() {
 }
 
-void DartTracingImpl::Initialize(mojo::ApplicationImpl* app) {
+void DartTracingImpl::Initialize(mojo::Shell* shell) {
   tracing::TraceProviderRegistryPtr registry;
-  ConnectToService(app->shell(), "mojo:tracing", GetProxy(&registry));
+  ConnectToService(shell, "mojo:tracing", GetProxy(&registry));
 
   mojo::InterfaceHandle<tracing::TraceProvider> provider;
   provider_impl_.Bind(GetProxy(&provider));