Enable startup profiling by Win x64 stack sampling profiler

base/profiler/stack_sampling_profiler.cc

Index: base/profiler/stack_sampling_profiler.cc
diff --git a/base/profiler/stack_sampling_profiler.cc b/base/profiler/stack_sampling_profiler.cc
index f7605079953769e162aa7463ebc54c6ea772485a..c5c284763fcd1ea708ca33c067e675085f907f93 100644
--- a/base/profiler/stack_sampling_profiler.cc
+++ b/base/profiler/stack_sampling_profiler.cc
@@ -19,49 +19,94 @@ namespace base {
 
 namespace {
 
-// Thread-safe singleton class that stores collected 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();
-  ~PendingProfiles();
+  using CompletedCallback = StackSamplingProfiler::CompletedCallback;
 
-  static PendingProfiles* GetInstance();
+  DefaultProfileProcessor();
+  ~DefaultProfileProcessor();
 
-  // Appends |profiles|. This function is thread safe.
-  void PutProfiles(const std::vector<StackSamplingProfiler::Profile>& profiles);
-  // Gets the pending profiles into *|profiles|. This function is thread safe.
-  void GetProfiles(std::vector<StackSamplingProfiler::Profile>* 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 std::vector<StackSamplingProfiler::Profile>& profiles);
 
  private:
+  // Gets the pending profiles into *|profiles|, with proper locking.
+  void GetProfiles(std::vector<StackSamplingProfiler::Profile>* profiles);
+
+  // Gets the current completed callback, with proper locking.
+  CompletedCallback GetCompletedCallback() const;
+
+  mutable Lock callback_lock_;
+  CompletedCallback default_completed_callback_;
+
   Lock profiles_lock_;
   std::vector<StackSamplingProfiler::Profile> profiles_;
 
-  DISALLOW_COPY_AND_ASSIGN(PendingProfiles);
+  DISALLOW_COPY_AND_ASSIGN(DefaultProfileProcessor);
 };
 
-PendingProfiles::PendingProfiles() {}
+DefaultProfileProcessor::DefaultProfileProcessor() {}
 
-PendingProfiles::~PendingProfiles() {}
+DefaultProfileProcessor::~DefaultProfileProcessor() {}
 
 // static
-PendingProfiles* PendingProfiles::GetInstance() {
-  return Singleton<PendingProfiles>::get();
+DefaultProfileProcessor* DefaultProfileProcessor::GetInstance() {
+  return Singleton<DefaultProfileProcessor>::get();
 }
 
-void PendingProfiles::PutProfiles(
+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.
+    std::vector<StackSamplingProfiler::Profile> profiles;
+    GetProfiles(&profiles);
+    if (!profiles.empty())
+      callback.Run(profiles);
+  }
+}
+
+void DefaultProfileProcessor::ProcessProfiles(
     const std::vector<StackSamplingProfiler::Profile>& profiles) {
-  AutoLock scoped_lock(profiles_lock_);
-  profiles_.insert(profiles_.end(), profiles.begin(), profiles.end());
+  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::GetProfiles(
+void DefaultProfileProcessor::GetProfiles(
     std::vector<StackSamplingProfiler::Profile>* 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
 
 StackSamplingProfiler::Module::Module() : base_address(nullptr) {}
@@ -90,12 +135,11 @@ StackSamplingProfiler::Profile::~Profile() {}
 class StackSamplingProfiler::SamplingThread : public PlatformThread::Delegate {
  public:
   // Samples stacks using |native_sampler|. When complete, invokes
-  // |profiles_callback| with the collected profiles. |profiles_callback| must
-  // be thread-safe and may consume the contents of the vector.
-  SamplingThread(
-      scoped_ptr<NativeStackSampler> native_sampler,
-      const SamplingParams& params,
-      Callback<void(const std::vector<Profile>&)> completed_callback);
+  // |completed_callback| with the collected profiles. |completed_callback| must
+  // be thread-safe.
+  SamplingThread(scoped_ptr<NativeStackSampler> native_sampler,
+                 const SamplingParams& params,
+                 CompletedCallback completed_callback);
   ~SamplingThread() override;
 
   // Implementation of PlatformThread::Delegate:
@@ -108,7 +152,7 @@ class StackSamplingProfiler::SamplingThread : public PlatformThread::Delegate {
   // collected, or false if collection was stopped before it completed.
   bool CollectProfile(Profile* profile, TimeDelta* elapsed_time);
   // Collects profiles from all bursts, or until the sampling is stopped. If
-  // stopped before complete, |profiles| will contains only full bursts.
+  // stopped before complete, |profiles| will contain only full bursts.
   void CollectProfiles(std::vector<Profile>* profiles);
 
   scoped_ptr<NativeStackSampler> native_sampler_;
@@ -117,7 +161,7 @@ class StackSamplingProfiler::SamplingThread : public PlatformThread::Delegate {
 
   WaitableEvent stop_event_;
 
-  Callback<void(const std::vector<Profile>&)> completed_callback_;
+  CompletedCallback completed_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SamplingThread);
 };
@@ -125,7 +169,7 @@ class StackSamplingProfiler::SamplingThread : public PlatformThread::Delegate {
 StackSamplingProfiler::SamplingThread::SamplingThread(
     scoped_ptr<NativeStackSampler> native_sampler,
     const SamplingParams& params,
-    Callback<void(const std::vector<Profile>&)> completed_callback)
+    CompletedCallback completed_callback)
     : native_sampler_(native_sampler.Pass()),
       params_(params),
       stop_event_(false, false),
@@ -221,20 +265,26 @@ StackSamplingProfiler::StackSamplingProfiler(PlatformThreadId thread_id,
                                              const SamplingParams& params)
     : thread_id_(thread_id), params_(params) {}
 
+StackSamplingProfiler::StackSamplingProfiler(PlatformThreadId thread_id,
+                                             const SamplingParams& params,
+                                             CompletedCallback callback)
+    : thread_id_(thread_id), params_(params), completed_callback_(callback) {}
+
 StackSamplingProfiler::~StackSamplingProfiler() {}
 
 void StackSamplingProfiler::Start() {
-  native_sampler_ = NativeStackSampler::Create(thread_id_);
-  if (!native_sampler_)
+  scoped_ptr<NativeStackSampler> native_sampler(
+      NativeStackSampler::Create(thread_id_));
+  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::PutProfiles,
-                Unretained(PendingProfiles::GetInstance())) :
-           custom_completed_callback_)));
+      new SamplingThread(native_sampler.Pass(), params_, callback));
   if (!PlatformThread::CreateNonJoinable(0, sampling_thread_.get()))
     LOG(ERROR) << "failed to create thread";
 }
@@ -245,13 +295,9 @@ void StackSamplingProfiler::Stop() {
 }
 
 // static
-void StackSamplingProfiler::GetPendingProfiles(std::vector<Profile>* profiles) {
-  PendingProfiles::GetInstance()->GetProfiles(profiles);
-}
-
-void StackSamplingProfiler::SetCustomCompletedCallback(
-    Callback<void(const std::vector<Profile>&)> callback) {
-  custom_completed_callback_ = callback;
+void StackSamplingProfiler::SetDefaultCompletedCallback(
+    CompletedCallback callback) {
+  DefaultProfileProcessor::GetInstance()->SetCompletedCallback(callback);
 }
 
 bool operator==(const StackSamplingProfiler::Frame &a,