Fix crashes in TracingBrowserTest.TestMemoryInfra

chrome/test/base/tracing.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_TEST_BASE_TRACING_H_
 #define CHROME_TEST_BASE_TRACING_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 14 matching lines @@
 // Example: BeginTracing("-excluded_category1,-excluded_category2");
 //
 // See base/trace_event/trace_event.h for documentation of included and excluded
 // category_patterns.
 bool BeginTracing(const std::string& category_patterns) WARN_UNUSED_RESULT;
 
 // Called from UI thread.
 // Begin tracing specified category_patterns on the browser.
 // |trace_config| specifies the configuration for tracing. This includes the
 // list of categories enabled, tracing modes and memory dumps configuration.
+// Once all child processes have acked to the StartTracing request,
+// |start_tracing_done_callback| will be called back.
 //
 // See base/trace_event/trace_config.h for documentation of configurations.
 bool BeginTracingWithTraceConfig(
     const base::trace_event::TraceConfig& trace_config) WARN_UNUSED_RESULT;
 
+typedef base::Callback<void()> StartTracingDoneCallback;
+bool BeginTracingWithTraceConfig(
+    const base::trace_event::TraceConfig& trace_config,
+    StartTracingDoneCallback start_tracing_done_callback) WARN_UNUSED_RESULT;
+
 // Called from UI thread.
 // End trace and collect the trace output as a json string.
 bool EndTracing(std::string* json_trace_output) WARN_UNUSED_RESULT;
 
 }  // namespace tracing
 
 #endif  // CHROME_TEST_BASE_TRACING_H_