Teach the mojo_shell --trace-startup flag to gather data from services

sky/tools/debugger/debugger.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/profiler.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
@@ skipping 10 matching lines @@
 #include "mojo/services/window_manager/public/interfaces/window_manager.mojom.h"
 #include "services/tracing/tracing.mojom.h"
 #include "sky/tools/debugger/trace_collector.h"
 
 namespace sky {
 namespace debugger {
 
 class SkyDebugger : public mojo::ApplicationDelegate,
                     public http_server::HttpHandler {
  public:
-  SkyDebugger() : is_tracing_(false), handler_binding_(this) {}
+  SkyDebugger() : is_tracing_(false), app_(nullptr), handler_binding_(this) {}
   ~SkyDebugger() override {}
 
  private:
   // mojo::ApplicationDelegate:
   void Initialize(mojo::ApplicationImpl* app) override {
-    app->ConnectToService("mojo:tracing", &tracing_);
+    app_ = app;
     app->ConnectToService("mojo:window_manager", &window_manager_);
 
     // Format: --args-for="app_url command_port"
     if (app->args().size() < 2) {
       LOG(ERROR) << "--args-for required to specify command_port";
       mojo::ApplicationImpl::Terminate();
       return;
     }
     base::StringToUint(app->args()[1], &command_port_);
     http_server::HttpServerFactoryPtr http_server_factory;
@@ skipping 85 matching lines @@
     // TODO(eseidel): We should orderly shutdown once mojo can.
     exit(0);
   }
 
   void StartTracing(const HandleRequestCallback& callback) {
     if (is_tracing_) {
       Error(callback, "Already tracing. Use stop_tracing to stop.\n");
       return;
     }
 
+    if (!tracing_)
+      app_->ConnectToService("mojo:tracing", &tracing_);
     is_tracing_ = true;
     mojo::DataPipe pipe;
     tracing_->Start(pipe.producer_handle.Pass(), mojo::String("*"));
     trace_collector_.reset(new TraceCollector(pipe.consumer_handle.Pass()));
     Respond(callback, "Starting trace (type 'stop_tracing' to stop)\n");
   }
 
   void StopTracing(const HandleRequestCallback& callback) {
     if (!is_tracing_) {
       Error(callback, "Not tracing yet. Use start_tracing to start.\n");
@@ skipping 25 matching lines @@
   void StopProfiling(const HandleRequestCallback& callback) {
     if (!base::debug::BeingProfiled()) {
       Error(callback, "Profiling not started");
       return;
     }
     base::debug::StopProfiling();
     Respond(callback, "Stopped profiling");
   }
 
   bool is_tracing_;
+  mojo::ApplicationImpl* app_;
   mojo::WindowManagerPtr window_manager_;
   tracing::TraceCoordinatorPtr tracing_;
   std::string url_;
   uint32_t command_port_;
 
   http_server::HttpServerPtr http_server_;
   mojo::Binding<http_server::HttpHandler> handler_binding_;
 
   scoped_ptr<TraceCollector> trace_collector_;
 
   DISALLOW_COPY_AND_ASSIGN(SkyDebugger);
 };
 
 }  // namespace debugger
 }  // namespace sky
 
 MojoResult MojoMain(MojoHandle application_request) {
   mojo::ApplicationRunnerChromium runner(new sky::debugger::SkyDebugger);
   runner.set_message_loop_type(base::MessageLoop::TYPE_IO);
   return runner.Run(application_request);
 }