Add tracing service and make the shell+sky_viewer+services talk to it

mojo/shell/context.cc

Index: mojo/shell/context.cc
diff --git a/mojo/shell/context.cc b/mojo/shell/context.cc
index 6b6ce247d4c6939b2814cd0ea48f7b324bd9e1dc..ff30bcc7cf755e63d49d818da17dd7194ec846c1 100644
--- a/mojo/shell/context.cc
+++ b/mojo/shell/context.cc
@@ -18,6 +18,7 @@
 #include "mojo/application_manager/application_loader.h"
 #include "mojo/application_manager/application_manager.h"
 #include "mojo/application_manager/background_shell_application_loader.h"
+#include "mojo/common/tracing_impl.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/simple_platform_support.h"
 #include "mojo/public/cpp/application/application_connection.h"
@@ -30,6 +31,8 @@
 #include "mojo/shell/switches.h"
 #include "mojo/shell/ui_application_loader_android.h"
 #include "mojo/spy/spy.h"
+#include "services/tracing/tracing.mojom.h"
+#include "url/gurl.h"
 
 #if defined(OS_ANDROID)
 #include "mojo/services/gles2/gpu_impl.h"
@@ -271,6 +274,11 @@ bool Context::Init() {
   }
 #endif
 
+  tracing::TraceDataCollectorPtr trace_data_collector_ptr;
+  application_manager_.ConnectToService(GURL("mojo:tracing"),
+                                        &trace_data_collector_ptr);
+  TracingImpl::Create(trace_data_collector_ptr.Pass());
+
   if (listener_)
     listener_->WaitForListening();