Add --trace-rotate-startup-file option and store unsaved trace data on exit.

content/browser/browser_main_runner.cc

Index: content/browser/browser_main_runner.cc
diff --git a/content/browser/browser_main_runner.cc b/content/browser/browser_main_runner.cc
index 16309dec8460af490e891e47ace869c483d258c5..7b98d4ac38b85f946e42c44ee9c53adae0fce6d9 100644
--- a/content/browser/browser_main_runner.cc
+++ b/content/browser/browser_main_runner.cc
@@ -130,13 +130,23 @@ class BrowserMainRunnerImpl : public BrowserMainRunner {
     // If leaks are found, the process will exit here.
     __lsan_do_leak_check();
 #endif
+    // If startup tracing has not been finished yet, replace it's dumper.
+    scoped_ptr<BrowserShutdownProfileDumper> startup_profiler;
+    if (main_loop_->is_tracing_startup()) {
+      startup_profiler.reset(
+          new BrowserShutdownProfileDumper(main_loop_->startup_trace_file()));
+      main_loop_->StopStartupTracingTimer();
+    }
+
     // The shutdown tracing got enabled in AttemptUserExit earlier, but someone
     // needs to write the result to disc. For that a dumper needs to get created
     // which will dump the traces to disc when it gets destroyed.
     const CommandLine& command_line = *CommandLine::ForCurrentProcess();
-    scoped_ptr<BrowserShutdownProfileDumper> profiler;
-    if (command_line.HasSwitch(switches::kTraceShutdown))
-      profiler.reset(new BrowserShutdownProfileDumper());
+    scoped_ptr<BrowserShutdownProfileDumper> shutdown_profiler;
+    if (command_line.HasSwitch(switches::kTraceShutdown)) {
+      shutdown_profiler.reset(
+          new BrowserShutdownProfileDumper(GetShutdownProfileFileName()));
+    }
 
     {
       // The trace event has to stay between profiler creation and destruction.
@@ -159,6 +169,19 @@ class BrowserMainRunnerImpl : public BrowserMainRunner {
   }
 
  protected:
+  // Returns the file name where we should save the shutdown trace dump to.
+  static base::FilePath GetShutdownProfileFileName() {
+    const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+    base::FilePath trace_file =
+        command_line.GetSwitchValuePath(switches::kTraceShutdownFile);
+
+    if (!trace_file.empty())
+      return trace_file;
+
+    // Default to saving the startup trace into the current dir.
+    return base::FilePath().AppendASCII("chrometrace.log");
+  }
+
   // True if we have started to initialize the runner.
   bool initialization_started_;