Add process lifetime annotations to stack samples.

base/profiler/native_stack_sampler.h

 // Copyright 2015 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 BASE_PROFILER_NATIVE_STACK_SAMPLER_H_
 #define BASE_PROFILER_NATIVE_STACK_SAMPLER_H_
 
 #include <memory>
 
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/profiler/stack_sampling_profiler.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 
 class NativeStackSamplerTestDelegate;
 
 // NativeStackSampler is an implementation detail of StackSamplingProfiler. It
 // abstracts the native implementation required to record a stack sample for a
 // given thread.
 class NativeStackSampler {
  public:
+  // The callback type used to add annotations to a sample during collection.
+  // This is passed to the native sampler to be applied at the most appropriate
+  // time. It is a simple function-pointer because the generated code must be
+  // completely predictable and do nothing that could acquire a mutex; a
+  // Callback object is code outside the control of this object and could,
+  // for example, acquire a mutex as part of allocating memory for a LOG
+  // message.
+  using AnnotateCallback = void (*)(StackSamplingProfiler::Sample*);
+
   virtual ~NativeStackSampler();
 
   // Creates a stack sampler that records samples for |thread_handle|. Returns
   // null if this platform does not support stack sampling.
   static std::unique_ptr<NativeStackSampler> Create(
       PlatformThreadId thread_id,
+      AnnotateCallback annotator,
       NativeStackSamplerTestDelegate* test_delegate);
 
   // The following functions are all called on the SamplingThread (not the
   // thread being sampled).
 
   // Notifies the sampler that we're starting to record a new profile. Modules
   // shared across samples in the profile should be recorded in |modules|.
   virtual void ProfileRecordingStarting(
       std::vector<StackSamplingProfiler::Module>* modules) = 0;
 
@@ skipping 25 matching lines @@
   NativeStackSamplerTestDelegate();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NativeStackSamplerTestDelegate);
 };
 
 }  // namespace base
 
 #endif  // BASE_PROFILER_NATIVE_STACK_SAMPLER_H_