Enable startup profiling by Win x64 stack sampling profiler

Collects stack samples at 10 Hz for 30 seconds at startup. Uploading of
samples to UMA is controlled by a Finch experiment.

This change moves to a callback-based mechanism for communicating
completed profiles to the metrics provider to avoid profiles lingering
in memory when reporting is disabled.

BUG=464929

Review URL: https://codereview.chromium.org/1029653002

Cr-Commit-Position: refs/heads/master@{#324175}

3 files changed, 269 insertions, 91 deletions

diff --git a/base/profiler/stack_sampling_profiler.cc b/base/profiler/stack_sampling_profiler.cc
index 317400b..1c08234 100644
--- a/base/profiler/stack_sampling_profiler.cc
+++ b/base/profiler/stack_sampling_profiler.cc
@@ -15,61 +15,102 @@
 
 namespace base {
 
-// PendingProfiles ------------------------------------------------------------
+// DefaultProfileProcessor ----------------------------------------------------
 
 namespace {
 
-// Thread-safe singleton class that stores collected call stack profiles waiting
-// to be processed.
-class PendingProfiles {
+// Singleton class responsible for providing the default processing for profiles
+// (i.e. for profiles generated by profilers without their own completed
+// callback).
+class DefaultProfileProcessor {
  public:
-  ~PendingProfiles();
+  using CompletedCallback = StackSamplingProfiler::CompletedCallback;
 
-  static PendingProfiles* GetInstance();
+  ~DefaultProfileProcessor();
 
-  // Appends |profiles| to |profiles_|. This function may be called on any
-  // thread.
-  void AppendProfiles(
-      const std::vector<StackSamplingProfiler::CallStackProfile>& profiles);
+  static DefaultProfileProcessor* GetInstance();
+
+  // Sets the callback to use for processing profiles captured without a
+  // per-profiler completed callback. Pending completed profiles are stored in
+  // this object until a non-null callback is provided here. This function is
+  // thread-safe.
+  void SetCompletedCallback(CompletedCallback callback);
+
+  // Processes |profiles|. This function is thread safe.
+  void ProcessProfiles(
+      const StackSamplingProfiler::CallStackProfiles& profiles);
+
+ private:
+  friend struct DefaultSingletonTraits<DefaultProfileProcessor>;
+
+  DefaultProfileProcessor();
 
   // Copies the pending profiles from |profiles_| into |profiles|, and clears
   // |profiles_|. This function may be called on any thread.
   void GetAndClearPendingProfiles(
-      std::vector<StackSamplingProfiler::CallStackProfile>* profiles);
+      StackSamplingProfiler::CallStackProfiles* profiles);
 
- private:
-  friend struct DefaultSingletonTraits<PendingProfiles>;
+  // Gets the current completed callback, with proper locking.
+  CompletedCallback GetCompletedCallback() const;
 
-  PendingProfiles();
+  mutable Lock callback_lock_;
+  CompletedCallback default_completed_callback_;
 
   Lock profiles_lock_;
-  std::vector<StackSamplingProfiler::CallStackProfile> profiles_;
+  StackSamplingProfiler::CallStackProfiles profiles_;
 
-  DISALLOW_COPY_AND_ASSIGN(PendingProfiles);
+  DISALLOW_COPY_AND_ASSIGN(DefaultProfileProcessor);
 };
 
-PendingProfiles::PendingProfiles() {}
-
-PendingProfiles::~PendingProfiles() {}
+DefaultProfileProcessor::~DefaultProfileProcessor() {}
 
 // static
-PendingProfiles* PendingProfiles::GetInstance() {
-  return Singleton<PendingProfiles>::get();
+DefaultProfileProcessor* DefaultProfileProcessor::GetInstance() {
+  return Singleton<DefaultProfileProcessor>::get();
 }
 
-void PendingProfiles::AppendProfiles(
-    const std::vector<StackSamplingProfiler::CallStackProfile>& profiles) {
-  AutoLock scoped_lock(profiles_lock_);
-  profiles_.insert(profiles_.end(), profiles.begin(), profiles.end());
+void DefaultProfileProcessor::SetCompletedCallback(CompletedCallback callback) {
+  {
+    AutoLock scoped_lock(callback_lock_);
+    default_completed_callback_ = callback;
+  }
+
+  if (!callback.is_null()) {
+    // Provide any pending profiles to the callback immediately.
+    StackSamplingProfiler::CallStackProfiles profiles;
+    GetAndClearPendingProfiles(&profiles);
+    if (!profiles.empty())
+      callback.Run(profiles);
+  }
+}
+
+void DefaultProfileProcessor::ProcessProfiles(
+    const StackSamplingProfiler::CallStackProfiles& profiles) {
+  CompletedCallback callback = GetCompletedCallback();
+
+  // Store pending profiles if we don't have a valid callback.
+  if (!callback.is_null()) {
+    callback.Run(profiles);
+  } else {
+    AutoLock scoped_lock(profiles_lock_);
+    profiles_.insert(profiles_.end(), profiles.begin(), profiles.end());
+  }
 }
 
-void PendingProfiles::GetAndClearPendingProfiles(
-    std::vector<StackSamplingProfiler::CallStackProfile>* profiles) {
+DefaultProfileProcessor::DefaultProfileProcessor() {}
+
+void DefaultProfileProcessor::GetAndClearPendingProfiles(
+    StackSamplingProfiler::CallStackProfiles* profiles) {
   profiles->clear();
 
   AutoLock scoped_lock(profiles_lock_);
   profiles_.swap(*profiles);
 }
+DefaultProfileProcessor::CompletedCallback
+DefaultProfileProcessor::GetCompletedCallback() const {
+  AutoLock scoped_lock(callback_lock_);
+  return default_completed_callback_;
+}
 
 }  // namespace
 
@@ -209,7 +250,16 @@ StackSamplingProfiler::StackSamplingProfiler(PlatformThreadId thread_id,
                                              const SamplingParams& params)
     : thread_id_(thread_id), params_(params) {}
 
-StackSamplingProfiler::~StackSamplingProfiler() {}
+StackSamplingProfiler::StackSamplingProfiler(PlatformThreadId thread_id,
+                                             const SamplingParams& params,
+                                             CompletedCallback callback)
+    : thread_id_(thread_id), params_(params), completed_callback_(callback) {}
+
+StackSamplingProfiler::~StackSamplingProfiler() {
+  Stop();
+  if (!sampling_thread_handle_.is_null())
+    PlatformThread::Join(sampling_thread_handle_);
+}
 
 void StackSamplingProfiler::Start() {
   scoped_ptr<NativeStackSampler> native_sampler =
@@ -217,14 +267,14 @@ void StackSamplingProfiler::Start() {
   if (!native_sampler)
     return;
 
+  CompletedCallback callback =
+      !completed_callback_.is_null() ? completed_callback_ :
+      Bind(&DefaultProfileProcessor::ProcessProfiles,
+           Unretained(DefaultProfileProcessor::GetInstance()));
   sampling_thread_.reset(
-      new SamplingThread(
-          native_sampler.Pass(), params_,
-          (custom_completed_callback_.is_null() ?
-           Bind(&PendingProfiles::AppendProfiles,
-                Unretained(PendingProfiles::GetInstance())) :
-           custom_completed_callback_)));
-  if (!PlatformThread::CreateNonJoinable(0, sampling_thread_.get()))
+      new SamplingThread(native_sampler.Pass(), params_, callback));
+  if (!PlatformThread::Create(0, sampling_thread_.get(),
+                              &sampling_thread_handle_))
     sampling_thread_.reset();
 }
 
@@ -234,8 +284,9 @@ void StackSamplingProfiler::Stop() {
 }
 
 // static
-void StackSamplingProfiler::GetPendingProfiles(CallStackProfiles* profiles) {
-  PendingProfiles::GetInstance()->GetAndClearPendingProfiles(profiles);
+void StackSamplingProfiler::SetDefaultCompletedCallback(
+    CompletedCallback callback) {
+  DefaultProfileProcessor::GetInstance()->SetCompletedCallback(callback);
 }
 
 // StackSamplingProfiler::Frame global functions ------------------------------
diff --git a/base/profiler/stack_sampling_profiler.h b/base/profiler/stack_sampling_profiler.h
index bea266d..73dbec7 100644
--- a/base/profiler/stack_sampling_profiler.h
+++ b/base/profiler/stack_sampling_profiler.h
@@ -34,11 +34,12 @@ class NativeStackSampler;
 //   base::StackSamplingProfiler profiler(base::PlatformThread::CurrentId()),
 //       params);
 //
-//   // To process the call stack profiles within Chrome rather than via UMA,
-//   // set a custom completed callback:
+//   // Or, to process the profiles within Chrome rather than via UMA, use a
+//   // custom completed callback:
 //   base::StackStackSamplingProfiler::CompletedCallback
 //       thread_safe_callback = ...;
-//   profiler.SetCustomCompletedCallback(thread_safe_callback);
+//   base::StackSamplingProfiler profiler(base::PlatformThread::CurrentId()),
+//       params, thread_safe_callback);
 //
 //   profiler.Start();
 //   // ... work being done on the target thread here ...
@@ -49,13 +50,13 @@ class NativeStackSampler;
 // altered as desired.
 //
 // When all call stack profiles are complete or the profiler is stopped, if the
-// custom completed callback was set it is called from the profiler thread with
-// the completed profiles. A profile is considered complete if all requested
-// samples were recorded for the profile (i.e. it was not stopped
-// prematurely). If no callback was set, the completed profiles are stored
-// internally and retrieved for UMA through GetPendingProfiles().
-// GetPendingProfiles() should never be called by other code; to retrieve
-// profiles for in-process processing, set a completed callback.
+// custom completed callback was set it is called from a thread created by the
+// profiler with the completed profiles. A profile is considered complete if all
+// requested samples were recorded for the profile (i.e. it was not stopped
+// prematurely).  If no callback was set, the default completed callback will be
+// called with the profiles. It is expected that the the default completed
+// callback is set by the metrics system to allow profiles to be provided via
+// UMA.
 //
 // The results of the profiling are passed to the completed callback and consist
 // of a vector of CallStackProfiles. Each CallStackProfile corresponds to a
@@ -164,8 +165,14 @@ class BASE_EXPORT StackSamplingProfiler {
   // thread-safe callback implementation.
   using CompletedCallback = Callback<void(const CallStackProfiles&)>;
 
+  // Creates a profiler that sends completed profiles to the default completed
+  // callback.
   StackSamplingProfiler(PlatformThreadId thread_id,
                         const SamplingParams& params);
+  // Creates a profiler that sends completed profiles to |completed_callback|.
+  StackSamplingProfiler(PlatformThreadId thread_id,
+                        const SamplingParams& params,
+                        CompletedCallback callback);
   ~StackSamplingProfiler();
 
   // Initializes the profiler and starts sampling.
@@ -176,19 +183,14 @@ class BASE_EXPORT StackSamplingProfiler {
   // specified in the SamplingParams are completed.
   void Stop();
 
-  // Moves all pending call stack profiles from internal storage to
-  // |profiles|. This function is thread safe.
+  // Sets a callback to process profiles collected by profiler instances without
+  // a completed callback. Profiles are queued internally until a non-null
+  // callback is provided to this function,
   //
-  // ***This is intended for use only by UMA.*** Callers who want to process the
-  // collected profiles should use SetCustomCompletedCallback.
-  static void GetPendingProfiles(CallStackProfiles* call_stack_profiles);
-
-  // By default, collected call stack profiles are stored internally and can be
-  // retrieved by GetPendingProfiles. If a callback is provided via this
-  // function, however, it is called with the collected profiles instead.
-  void set_custom_completed_callback(CompletedCallback callback) {
-    custom_completed_callback_ = callback;
-  }
+  // The callback is typically called on a thread created by the profiler.  If
+  // completed profiles are queued when set, however, it will also be called
+  // immediately on the calling thread.
+  static void SetDefaultCompletedCallback(CompletedCallback callback);
 
  private:
   // SamplingThread is a separate thread used to suspend and sample stacks from
@@ -226,7 +228,7 @@ class BASE_EXPORT StackSamplingProfiler {
     // terminate before all the samples specified in |params_| are collected.
     WaitableEvent stop_event_;
 
-    CompletedCallback completed_callback_;
+    const CompletedCallback completed_callback_;
 
     DISALLOW_COPY_AND_ASSIGN(SamplingThread);
   };
@@ -237,8 +239,9 @@ class BASE_EXPORT StackSamplingProfiler {
   const SamplingParams params_;
 
   scoped_ptr<SamplingThread> sampling_thread_;
+  PlatformThreadHandle sampling_thread_handle_;
 
-  CompletedCallback custom_completed_callback_;
+  const CompletedCallback completed_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
 };
diff --git a/base/profiler/stack_sampling_profiler_unittest.cc b/base/profiler/stack_sampling_profiler_unittest.cc
index 5bfc2d4..e48c89b 100644
--- a/base/profiler/stack_sampling_profiler_unittest.cc
+++ b/base/profiler/stack_sampling_profiler_unittest.cc
@@ -14,10 +14,12 @@
 
 namespace base {
 
+using SamplingParams = StackSamplingProfiler::SamplingParams;
 using Frame = StackSamplingProfiler::Frame;
 using Module = StackSamplingProfiler::Module;
 using Sample = StackSamplingProfiler::Sample;
 using CallStackProfile = StackSamplingProfiler::CallStackProfile;
+using CallStackProfiles = StackSamplingProfiler::CallStackProfiles;
 
 namespace {
 
@@ -85,45 +87,99 @@ NOINLINE void TargetThread::SignalAndWaitUntilSignaled(
   ALLOW_UNUSED_LOCAL(x);
 }
 
+// Called on the profiler thread when complete, to collect profiles.
+void SaveProfiles(CallStackProfiles* profiles,
+                  const CallStackProfiles& pending_profiles) {
+  *profiles = pending_profiles;
+}
+
 // Called on the profiler thread when complete. Collects profiles produced by
 // the profiler, and signals an event to allow the main thread to know that that
 // the profiler is done.
-void SaveProfilesAndSignalEvent(
-    std::vector<CallStackProfile>* profiles,
-    WaitableEvent* event,
-    const std::vector<CallStackProfile>& pending_profiles) {
+void SaveProfilesAndSignalEvent(CallStackProfiles* profiles,
+                                WaitableEvent* event,
+                                const CallStackProfiles& pending_profiles) {
   *profiles = pending_profiles;
   event->Signal();
 }
 
-// Captures call stack profiles as specified by |params| on the TargetThread,
-// and returns them in |profiles|. Waits up to |profiler_wait_time| for the
-// profiler to complete.
-void CaptureProfiles(const StackSamplingProfiler::SamplingParams& params,
-                     std::vector<CallStackProfile>* profiles,
-                     TimeDelta profiler_wait_time) {
+// Executes the function with the target thread running and executing within
+// SignalAndWaitUntilSignaled(). Performs all necessary target thread startup
+// and shutdown work before and afterward.
+template <class Function>
+void WithTargetThread(Function function) {
   TargetThread target_thread;
   PlatformThreadHandle target_thread_handle;
   EXPECT_TRUE(PlatformThread::Create(0, &target_thread, &target_thread_handle));
 
   target_thread.WaitForThreadStart();
 
-  WaitableEvent sampling_thread_completed(true, false);
-  profiles->clear();
-  StackSamplingProfiler profiler(target_thread.id(), params);
-  profiler.set_custom_completed_callback(
-      Bind(&SaveProfilesAndSignalEvent, Unretained(profiles),
-           Unretained(&sampling_thread_completed)));
-  profiler.Start();
-  sampling_thread_completed.TimedWait(profiler_wait_time);
-  profiler.Stop();
-  sampling_thread_completed.Wait();
+  function(target_thread.id());
 
   target_thread.SignalThreadToFinish();
 
   PlatformThread::Join(target_thread_handle);
 }
 
+// Captures profiles as specified by |params| on the TargetThread, and returns
+// them in |profiles|. Waits up to |profiler_wait_time| for the profiler to
+// complete.
+void CaptureProfilesWithObjectCallback(const SamplingParams& params,
+                                       CallStackProfiles* profiles,
+                                       TimeDelta profiler_wait_time) {
+  profiles->clear();
+
+  WithTargetThread([&params, profiles, profiler_wait_time](
+      PlatformThreadId target_thread_id) {
+    WaitableEvent sampling_thread_completed(true, false);
+    const StackSamplingProfiler::CompletedCallback callback =
+        Bind(&SaveProfilesAndSignalEvent, Unretained(profiles),
+             Unretained(&sampling_thread_completed));
+    StackSamplingProfiler profiler(target_thread_id, params, callback);
+    profiler.Start();
+    sampling_thread_completed.TimedWait(profiler_wait_time);
+    profiler.Stop();
+    sampling_thread_completed.Wait();
+  });
+}
+
+// Captures profiles as specified by |params| on the TargetThread, and returns
+// them in |profiles|. Uses the default callback rather than a per-object
+// callback.
+void CaptureProfilesWithDefaultCallback(const SamplingParams& params,
+                                        CallStackProfiles* profiles) {
+  profiles->clear();
+
+  WithTargetThread([&params, profiles](PlatformThreadId target_thread_id) {
+    WaitableEvent sampling_thread_completed(false, false);
+    StackSamplingProfiler::SetDefaultCompletedCallback(
+        Bind(&SaveProfilesAndSignalEvent, Unretained(profiles),
+             Unretained(&sampling_thread_completed)));
+
+    StackSamplingProfiler profiler(target_thread_id, params);
+    profiler.Start();
+    sampling_thread_completed.Wait();
+
+    StackSamplingProfiler::SetDefaultCompletedCallback(
+        StackSamplingProfiler::CompletedCallback());
+  });
+}
+
+// Runs the profiler with |params| on the TargetThread, with no default or
+// per-object callback.
+void RunProfilerWithNoCallback(const SamplingParams& params,
+                               TimeDelta profiler_wait_time) {
+  WithTargetThread(
+      [&params, profiler_wait_time](PlatformThreadId target_thread_id) {
+        StackSamplingProfiler profiler(target_thread_id, params);
+        profiler.Start();
+        // Since we don't specify a callback, we don't have a synchronization
+        // mechanism with the sampling thread. Just sleep instead.
+        PlatformThread::Sleep(profiler_wait_time);
+        profiler.Stop();
+      });
+}
+
 // If this executable was linked with /INCREMENTAL (the default for non-official
 // debug and release builds on Windows), function addresses do not correspond to
 // function code itself, but instead to instructions in the Incremental Link
@@ -195,12 +251,12 @@ TimeDelta AVeryLongTimeDelta() { return TimeDelta::FromDays(1); }
 #define MAYBE_Basic DISABLED_Basic
 #endif
 TEST(StackSamplingProfilerTest, MAYBE_Basic) {
-  StackSamplingProfiler::SamplingParams params;
+  SamplingParams params;
   params.sampling_interval = TimeDelta::FromMilliseconds(0);
   params.samples_per_burst = 1;
 
   std::vector<CallStackProfile> profiles;
-  CaptureProfiles(params, &profiles, AVeryLongTimeDelta());
+  CaptureProfilesWithObjectCallback(params, &profiles, AVeryLongTimeDelta());
 
   // Check that the profile and samples sizes are correct, and the module
   // indices are in range.
@@ -244,14 +300,14 @@ TEST(StackSamplingProfilerTest, MAYBE_Basic) {
 #define MAYBE_MultipleProfilesAndSamples DISABLED_MultipleProfilesAndSamples
 #endif
 TEST(StackSamplingProfilerTest, MAYBE_MultipleProfilesAndSamples) {
-  StackSamplingProfiler::SamplingParams params;
+  SamplingParams params;
   params.burst_interval = params.sampling_interval =
       TimeDelta::FromMilliseconds(0);
   params.bursts = 2;
   params.samples_per_burst = 3;
 
   std::vector<CallStackProfile> profiles;
-  CaptureProfiles(params, &profiles, AVeryLongTimeDelta());
+  CaptureProfilesWithObjectCallback(params, &profiles, AVeryLongTimeDelta());
 
   ASSERT_EQ(2u, profiles.size());
   EXPECT_EQ(3u, profiles[0].samples.size());
@@ -266,11 +322,12 @@ TEST(StackSamplingProfilerTest, MAYBE_MultipleProfilesAndSamples) {
 #define MAYBE_StopDuringInitialDelay DISABLED_StopDuringInitialDelay
 #endif
 TEST(StackSamplingProfilerTest, MAYBE_StopDuringInitialDelay) {
-  StackSamplingProfiler::SamplingParams params;
+  SamplingParams params;
   params.initial_delay = TimeDelta::FromSeconds(60);
 
   std::vector<CallStackProfile> profiles;
-  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(0));
+  CaptureProfilesWithObjectCallback(params, &profiles,
+                                    TimeDelta::FromMilliseconds(0));
 
   EXPECT_TRUE(profiles.empty());
 }
@@ -283,14 +340,15 @@ TEST(StackSamplingProfilerTest, MAYBE_StopDuringInitialDelay) {
 #define MAYBE_StopDuringInterBurstInterval DISABLED_StopDuringInterBurstInterval
 #endif
 TEST(StackSamplingProfilerTest, MAYBE_StopDuringInterBurstInterval) {
-  StackSamplingProfiler::SamplingParams params;
+  SamplingParams params;
   params.sampling_interval = TimeDelta::FromMilliseconds(0);
   params.burst_interval = TimeDelta::FromSeconds(60);
   params.bursts = 2;
   params.samples_per_burst = 1;
 
   std::vector<CallStackProfile> profiles;
-  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(50));
+  CaptureProfilesWithObjectCallback(params, &profiles,
+                                    TimeDelta::FromMilliseconds(50));
 
   ASSERT_EQ(1u, profiles.size());
   EXPECT_EQ(1u, profiles[0].samples.size());
@@ -304,14 +362,80 @@ TEST(StackSamplingProfilerTest, MAYBE_StopDuringInterBurstInterval) {
   DISABLED_StopDuringInterSampleInterval
 #endif
 TEST(StackSamplingProfilerTest, MAYBE_StopDuringInterSampleInterval) {
-  StackSamplingProfiler::SamplingParams params;
+  SamplingParams params;
   params.sampling_interval = TimeDelta::FromSeconds(60);
   params.samples_per_burst = 2;
 
   std::vector<CallStackProfile> profiles;
-  CaptureProfiles(params, &profiles, TimeDelta::FromMilliseconds(50));
+  CaptureProfilesWithObjectCallback(params, &profiles,
+                                    TimeDelta::FromMilliseconds(50));
 
   EXPECT_TRUE(profiles.empty());
 }
 
+// Checks that profiles are captured via the default completed callback.
+#if defined(_WIN64)
+#define MAYBE_DefaultCallback DefaultCallback
+#else
+#define MAYBE_DefaultCallback DISABLED_DefaultCallback
+#endif
+TEST(StackSamplingProfilerTest, MAYBE_DefaultCallback) {
+  SamplingParams params;
+  params.samples_per_burst = 1;
+
+  CallStackProfiles profiles;
+  CaptureProfilesWithDefaultCallback(params, &profiles);
+
+  EXPECT_EQ(1u, profiles.size());
+  EXPECT_EQ(1u, profiles[0].samples.size());
+}
+
+// Checks that profiles are queued until a default callback is set, then
+// delivered.
+#if defined(_WIN64)
+#define MAYBE_ProfilesQueuedWithNoCallback ProfilesQueuedWithNoCallback
+#else
+#define MAYBE_ProfilesQueuedWithNoCallback DISABLED_ProfilesQueuedWithNoCallback
+#endif
+TEST(StackSamplingProfilerTest, MAYBE_ProfilesQueuedWithNoCallback) {
+  SamplingParams params;
+  params.samples_per_burst = 1;
+
+  RunProfilerWithNoCallback(params, TimeDelta::FromMilliseconds(50));
+
+  CallStackProfiles profiles;
+  // This should immediately call SaveProfiles on this thread.
+  StackSamplingProfiler::SetDefaultCompletedCallback(
+      Bind(&SaveProfiles, Unretained(&profiles)));
+  EXPECT_EQ(1u, profiles.size());
+  EXPECT_EQ(1u, profiles[0].samples.size());
+  StackSamplingProfiler::SetDefaultCompletedCallback(
+      StackSamplingProfiler::CompletedCallback());
+}
+
+// Checks that we can destroy the profiler while profiling.
+#if defined(_WIN64)
+#define MAYBE_DestroyProfilerWhileProfiling DestroyProfilerWhileProfiling
+#else
+#define MAYBE_DestroyProfilerWhileProfiling \
+  DISABLED_DestroyProfilerWhileProfiling
+#endif
+TEST(StackSamplingProfilerTest, MAYBE_DestroyProfilerWhileProfiling) {
+  SamplingParams params;
+  params.sampling_interval = TimeDelta::FromMilliseconds(10);
+
+  CallStackProfiles profiles;
+  WithTargetThread([&params, &profiles](PlatformThreadId target_thread_id) {
+    scoped_ptr<StackSamplingProfiler> profiler;
+    profiler.reset(new StackSamplingProfiler(
+        target_thread_id, params, Bind(&SaveProfiles, Unretained(&profiles))));
+    profiler->Start();
+    profiler.reset();
+
+    // Wait longer than a sample interval to catch any use-after-free actions by
+    // the profiler thread.
+    PlatformThread::Sleep(TimeDelta::FromMilliseconds(50));
+  });
+}
+
 }  // namespace base