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

sky/tools/debugger/prompt/prompt.cc

Index: sky/tools/debugger/prompt/prompt.cc
diff --git a/sky/tools/debugger/prompt/prompt.cc b/sky/tools/debugger/prompt/prompt.cc
index f400055ac22768684f66bcbff3270e0494aa0d75..6ef357d1d22183f997c0a9688d1511a52c24c379 100644
--- a/sky/tools/debugger/prompt/prompt.cc
+++ b/sky/tools/debugger/prompt/prompt.cc
@@ -5,10 +5,10 @@
 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
 #include "mojo/application/application_runner_chromium.h"
-#include "mojo/common/tracing.mojom.h"
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_delegate.h"
 #include "mojo/public/cpp/application/application_impl.h"
+#include "services/tracing/tracing.mojom.h"
 #include "sky/tools/debugger/debugger.mojom.h"
 #include <iostream>
 
@@ -42,7 +42,7 @@ class Prompt : public mojo::ApplicationDelegate {
  private:
   // Overridden from mojo::ApplicationDelegate:
   virtual void Initialize(mojo::ApplicationImpl* app) override {
-    app->ConnectToService("mojo:sky_viewer", &tracing_);
+    app->ConnectToService("mojo:tracing", &tracing_);
     if (app->args().size() > 1)
       url_ = app->args()[1];
     else {
@@ -138,17 +138,17 @@ class Prompt : public mojo::ApplicationDelegate {
   void ToggleTracing() {
     if (is_tracing_) {
       std::cout << "Stopping trace (writing to sky_viewer.trace)" << std::endl;
-      tracing_->Stop();
+      tracing_->StopAndFlush();
     } else {
       std::cout << "Starting trace (type 'trace' to stop tracing)" << std::endl;
-      tracing_->Start();
+      tracing_->Start(mojo::String("sky_viewer"), mojo::String("*"));
     }
     is_tracing_ = !is_tracing_;
   }
 
   bool is_tracing_;
   DebuggerPtr debugger_;
-  mojo::TracingPtr tracing_;
+  tracing::TraceCoordinatorPtr tracing_;
   std::string url_;
   base::WeakPtrFactory<Prompt> weak_ptr_factory_;