Add some trace points to mojo_shell for app lifetime

shell/application_manager/network_fetcher.cc

Index: shell/application_manager/network_fetcher.cc
diff --git a/shell/application_manager/network_fetcher.cc b/shell/application_manager/network_fetcher.cc
index 05aba7ab3605b5837b5acdb53e789b03f50c0246..470d2a374925c451b0887d6dbe302a86fb0198b4 100644
--- a/shell/application_manager/network_fetcher.cc
+++ b/shell/application_manager/network_fetcher.cc
@@ -14,6 +14,7 @@
 #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"
@@ -182,6 +183,8 @@ bool NetworkFetcher::PeekFirstLine(std::string* line) {
 
 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;
@@ -194,6 +197,7 @@ void NetworkFetcher::StartNetworkRequest(const GURL& url,
 }
 
 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 "