Perfetto: New switch for startup tracing directly to file

Reviewed as part of https://chromium-review.googlesource.com/c/chromium/src/+/1161541

TBR=skyostil@chromium.org

Change-Id: I81973d090fe632b63a2cb5d501f32df13de795e2
Reviewed-on: https://chromium-review.googlesource.com/c/1308656Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604045}

components/tracing/common/trace_startup.cc

@@ -19,6 +19,13 @@ void EnableStartupTracingIfNeeded() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
+  // TODO(oysteine): Startup tracing using Perfetto
+  // is enabled by the Mojo consumer in content/browser
+  // for now; this is too late in the browser startup
+  // process however.
+  if (command_line.HasSwitch(switches::kPerfettoOutputFile))
+    return;
+
   // Ensure TraceLog is initialized first.
   // https://crbug.com/764357
   base::trace_event::TraceLog::GetInstance();

components/tracing/common/tracing_switches.cc

@@ -54,6 +54,12 @@ const char kTraceStartupFile[]              = "trace-startup-file";
 // "record-until-full" mode will be used.
 const char kTraceStartupRecordMode[] = "trace-startup-record-mode";
 
+// If supplied, will enable Perfetto startup tracing and stream the
+// output to the given file.
+// TODO(oysteine): Remove once Perfetto starts early enough after
+// process startup to be able to replace the legacy startup tracing.
+const char kPerfettoOutputFile[] = "perfetto-output-file";
+
 // Sends a pretty-printed version of tracing info to the console.
 const char kTraceToConsole[]                = "trace-to-console";
 

components/tracing/common/tracing_switches.h

@@ -17,6 +17,7 @@ TRACING_EXPORT extern const char kTraceStartup[];
 TRACING_EXPORT extern const char kTraceStartupDuration[];
 TRACING_EXPORT extern const char kTraceStartupFile[];
 TRACING_EXPORT extern const char kTraceStartupRecordMode[];
+TRACING_EXPORT extern const char kPerfettoOutputFile[];
 TRACING_EXPORT extern const char kTraceToConsole[];
 TRACING_EXPORT extern const char kTraceUploadURL[];