Wait for sampling to complete before destructing.

base/profiler/stack_sampling_profiler.h

Index: base/profiler/stack_sampling_profiler.h
diff --git a/base/profiler/stack_sampling_profiler.h b/base/profiler/stack_sampling_profiler.h
index 9489fd0bc128a16cd93707228f72c82b1c462a77..d33ee2525ce0472f7442d908526a086656947ee2 100644
--- a/base/profiler/stack_sampling_profiler.h
+++ b/base/profiler/stack_sampling_profiler.h
@@ -25,12 +25,19 @@ namespace base {
 
 class NativeStackSampler;
 class NativeStackSamplerTestDelegate;
+class WaitableEvent;
 
 // StackSamplingProfiler periodically stops a thread to sample its stack, for
 // the purpose of collecting information about which code paths are
 // executing. This information is used in aggregate by UMA to identify hot
 // and/or janky code paths.
 //
+// IMPORTANT: Only threads guaranteed to live beyond the lifetime of the
+// profiler object can be safely sampled. Sampling the activity of the current
+// thread within the scope of this object is safe, but sampling any other
+// thread could cause Bad Things(tm) to occur should that thread exit before
+// sampling is complete. USE WITH CAUTION!
+//
 // Sample StackSamplingProfiler usage:
 //
 //   // Create and customize params as desired.
@@ -205,21 +212,15 @@ class BASE_EXPORT StackSamplingProfiler {
   // Stops any profiling currently taking place before destroying the profiler.
   ~StackSamplingProfiler();
 
-  // The fire-and-forget interface: starts a profiler and allows it to complete
-  // without the caller needing to manage the profiler lifetime. May be invoked
-  // from any thread, but requires that the calling thread has a message loop.
-  static void StartAndRunAsync(PlatformThreadId thread_id,
-                               const SamplingParams& params,
-                               const CompletedCallback& callback);
-
   // Initializes the profiler and starts sampling.
   void Start();
 
   // Stops the profiler and any ongoing sampling. Calling this function is
   // optional; if not invoked profiling terminates when all the profiling bursts
   // specified in the SamplingParams are completed or the profiler is destroyed,
-  // whichever occurs first.
-  void Stop();
+  // whichever occurs first. If |done| is not null, a signal will be sent to it
+  // once the sampling has stopped and the callback completed.
+  void Stop(WaitableEvent* done);
 
   // Stops all active profiles and cleans up any resources in anticipation of
   // a shutdown of the current process.