Add some trace points to mojo_shell for app lifetime

shell/application_manager/network_fetcher.cc

 // Copyright 2015 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 "shell/application_manager/network_fetcher.h"
 
 #include "base/bind.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/process/process.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/trace_event/trace_event.h"
 #include "crypto/secure_hash.h"
 #include "crypto/sha2.h"
 #include "mojo/common/common_type_converters.h"
 #include "mojo/common/data_pipe_utils.h"
 #include "mojo/services/network/public/interfaces/network_service.mojom.h"
 #include "shell/application_manager/data_pipe_peek.h"
 
 namespace mojo {
 namespace shell {
 
@@ skipping 148 matching lines @@
          magic == kMojoMagic;
 }
 
 bool NetworkFetcher::PeekFirstLine(std::string* line) {
   return BlockingPeekLine(response_->body.get(), line, kMaxShebangLength,
                           kPeekTimeout);
 }
 
 void NetworkFetcher::StartNetworkRequest(const GURL& url,
                                          NetworkService* network_service) {
+  TRACE_EVENT_ASYNC_BEGIN0("mojo_shell", "NetworkFetcher::NetworkRequest",

[viettrungluu, 2015/03/24 20:04:34]

Maybe also record the url here?

[jamesr, 2015/03/27 20:42:21]

Done.

+                           this);
   URLRequestPtr request(URLRequest::New());
   request->url = String::From(url);
   request->auto_follow_redirects = false;
   request->bypass_cache = disable_cache_;
 
   network_service->CreateURLLoader(GetProxy(&url_loader_));
   url_loader_->Start(request.Pass(),
                      base::Bind(&NetworkFetcher::OnLoadComplete,
                                 weak_ptr_factory_.GetWeakPtr()));
 }
 
 void NetworkFetcher::OnLoadComplete(URLResponsePtr response) {
+  TRACE_EVENT_ASYNC_END0("mojo_shell", "NetworkFetcher::NetworkRequest", this);
   if (response->error) {
     LOG(ERROR) << "Error (" << response->error->code << ": "
                << response->error->description << ") while fetching "
                << response->url;
     loader_callback_.Run(make_scoped_ptr<Fetcher>(NULL));
     return;
   }
 
   if (response->status_code >= 400 && response->status_code < 600) {
     LOG(ERROR) << "Error (" << response->status_code << ": "
                << response->status_line << "): "
                << "while fetching " << response->url;
     loader_callback_.Run(make_scoped_ptr<Fetcher>(NULL));
     return;
   }
 
   response_ = response.Pass();
   loader_callback_.Run(make_scoped_ptr(this));
 }
 
 }  // namespace shell
 }  // namespace mojo