Add shell::Tracer object and wire up to --trace-startup on Android

shell/desktop/main.cc

 // Copyright 2013 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 <stdio.h>
 #include <string.h>
 
 #include <algorithm>
 #include <iostream>
 
 #include "base/at_exit.h"
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/profiler.h"
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/trace_event/trace_event.h"
 #include "shell/child_main.h"
 #include "shell/command_line_util.h"
 #include "shell/context.h"
 #include "shell/init.h"
 #include "shell/switches.h"
+#include "shell/tracer.h"
 
 namespace {
 
 void Usage() {
   std::cerr << "Launch Mojo applications.\n";
   std::cerr
       << "Usage: mojo_shell"
       << " [--" << switches::kArgsFor << "=<mojo-app>]"
       << " [--" << switches::kContentHandlers << "=<handlers>]"
       << " [--" << switches::kCPUProfile << "]"
       << " [--" << switches::kEnableExternalApplications << "]"
       << " [--" << switches::kDisableCache << "]"
       << " [--" << switches::kEnableMultiprocess << "]"
       << " [--" << switches::kOrigin << "=<url-lib-path>]"
       << " [--" << switches::kTraceStartup << "]"
       << " [--" << switches::kURLMappings << "=from1=to1,from2=to2]"
       << " [--" << switches::kPredictableAppFilenames << "]"
       << " [--" << switches::kWaitForDebugger << "]"
       << " <mojo-app> ...\n\n"
       << "A <mojo-app> is a Mojo URL or a Mojo URL and arguments within "
       << "quotes.\n"
       << "Example: mojo_shell \"mojo:js_standalone test.js\".\n"
       << "<url-lib-path> is searched for shared libraries named by mojo URLs.\n"
       << "The value of <handlers> is a comma separated list like:\n"
       << "text/html,mojo:html_viewer,"
       << "application/javascript,mojo:js_content_handler\n";
 }
 
-// Whether we're currently tracing.
-bool g_tracing = false;
-
-// Number of tracing blocks written.
-uint32_t g_blocks = 0;
-
-// Trace file, if open.
-FILE* g_trace_file = nullptr;
-
-void WriteTraceDataCollected(
-    base::WaitableEvent* event,
-    const scoped_refptr<base::RefCountedString>& events_str,
-    bool has_more_events) {
-  if (g_blocks) {
-    fwrite(",", 1, 1, g_trace_file);
-  }
-
-  ++g_blocks;
-  fwrite(events_str->data().c_str(), 1, events_str->data().length(),
-         g_trace_file);
-  if (!has_more_events) {
-    static const char kEnd[] = "]}";
-    fwrite(kEnd, 1, strlen(kEnd), g_trace_file);
-    PCHECK(fclose(g_trace_file) == 0);
-    g_trace_file = nullptr;
-    event->Signal();
-  }
-}
-
-void EndTraceAndFlush(base::WaitableEvent* event) {
-  g_trace_file = fopen("mojo_shell.trace", "w+");
-  PCHECK(g_trace_file);
-  static const char kStart[] = "{\"traceEvents\":[";
-  fwrite(kStart, 1, strlen(kStart), g_trace_file);
-  base::trace_event::TraceLog::GetInstance()->SetDisabled();
-  base::trace_event::TraceLog::GetInstance()->Flush(
-      base::Bind(&WriteTraceDataCollected, base::Unretained(event)));
-}
-
-void StopTracingAndFlushToDisk() {
-  g_tracing = false;
-  base::trace_event::TraceLog::GetInstance()->SetDisabled();
-  base::WaitableEvent flush_complete_event(false, false);
-  // TraceLog::Flush requires a message loop but we've already shut ours down.
-  // Spin up a new thread to flush things out.
-  base::Thread flush_thread("mojo_shell_trace_event_flush");
-  flush_thread.Start();
-  flush_thread.message_loop()->PostTask(
-      FROM_HERE,
-      base::Bind(EndTraceAndFlush, base::Unretained(&flush_complete_event)));
-  flush_complete_event.Wait();
-}
-
 }  // namespace
 
 int main(int argc, char** argv) {
   base::AtExitManager at_exit;
   base::CommandLine::Init(argc, argv);
 
+  shell::Tracer tracer;
+
   mojo::shell::InitializeLogging();
 
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   // TODO(vtl): Unify parent and child process cases to the extent possible.
   int exit_code = 0;
   if (command_line.HasSwitch(switches::kChildProcess)) {
     exit_code = mojo::shell::ChildMain();
   } else {
     // Only check the command line for the main process.
     const std::set<std::string> all_switches = switches::GetAllSwitches();
     const base::CommandLine::SwitchMap switches = command_line.GetSwitches();
     bool found_unknown_switch = false;
     for (const auto& s : switches) {
       if (all_switches.find(s.first) == all_switches.end()) {
         std::cerr << "unknown switch: " << s.first << std::endl;
         found_unknown_switch = true;
       }
     }
 
     if (found_unknown_switch ||
         (!command_line.HasSwitch(switches::kEnableExternalApplications) &&
          (command_line.HasSwitch(switches::kHelp) ||
           command_line.GetArgs().empty()))) {
       Usage();
       return 0;
     }
 
-    if (command_line.HasSwitch(switches::kTraceStartup)) {
-      g_tracing = true;
-      base::trace_event::CategoryFilter category_filter(
-          command_line.GetSwitchValueASCII(switches::kTraceStartup));
-      base::trace_event::TraceLog::GetInstance()->SetEnabled(
-          category_filter, base::trace_event::TraceLog::RECORDING_MODE,
-          base::trace_event::TraceOptions(
-              base::trace_event::RECORD_UNTIL_FULL));
-    }
+    bool trace_startup = command_line.HasSwitch(switches::kTraceStartup);
+    if (trace_startup)
+      tracer.Start(command_line.GetSwitchValueASCII(switches::kTraceStartup));
 
     if (command_line.HasSwitch(switches::kCPUProfile)) {
 #if !defined(NDEBUG) || !defined(ENABLE_PROFILING)
       LOG(ERROR) << "Profiling requires is_debug=false and "
                  << "enable_profiling=true. Continuing without profiling.";
 // StartProfiling() and StopProfiling() are a no-op.
 #endif
       base::debug::StartProfiling("mojo_shell.pprof");
     }
 
     // We want the shell::Context to outlive the MessageLoop so that pipes are
     // all gracefully closed / error-out before we try to shut the Context down.
     mojo::shell::Context shell_context;
     {
       base::MessageLoop message_loop;
       if (!shell_context.Init()) {
         Usage();
         return 0;
       }
-      if (g_tracing) {
-        message_loop.PostDelayedTask(FROM_HERE,
-                                     base::Bind(StopTracingAndFlushToDisk),
-                                     base::TimeDelta::FromSeconds(5));
+      if (trace_startup) {
+        message_loop.PostDelayedTask(
+            FROM_HERE,
+            base::Bind(&shell::Tracer::StopAndFlushToFile,
+                       base::Unretained(&tracer), "mojo_shell.trace"),
+            base::TimeDelta::FromSeconds(5));
       }
 
       // The mojo_shell --args-for command-line switch is handled specially
       // because it can appear more than once. The base::CommandLine class
       // collapses multiple occurrences of the same switch.
       for (int i = 1; i < argc; i++) {
         ApplyApplicationArgs(&shell_context, argv[i]);
       }
 
       message_loop.PostTask(
           FROM_HERE,
           base::Bind(&mojo::shell::RunCommandLineApps, &shell_context));
       message_loop.Run();
 
       // Must be called before |message_loop| is destroyed.
       shell_context.Shutdown();
     }
 
     if (command_line.HasSwitch(switches::kCPUProfile)) {
       base::debug::StopProfiling();
     }
   }
 
-  if (g_tracing)
-    StopTracingAndFlushToDisk();
+  tracer.StopAndFlushToFile("mojo_shell.trace");
   return exit_code;
 }