Fix crashes in TracingBrowserTest.TestMemoryInfra

chrome/test/base/tracing.h

Index: chrome/test/base/tracing.h
diff --git a/chrome/test/base/tracing.h b/chrome/test/base/tracing.h
index 9c87927e3626143790c205e6d25eb28135765c60..115597b48ec251dc025ab7dbb9dadbd85c64eebf 100644
--- a/chrome/test/base/tracing.h
+++ b/chrome/test/base/tracing.h
@@ -32,11 +32,18 @@ bool BeginTracing(const std::string& category_patterns) WARN_UNUSED_RESULT;
 // 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;