Stack sampling profiler: handle unloaded and unloading modules

base/profiler/stack_sampling_profiler.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_STACK_SAMPLING_PROFILER_H_
 #define BASE_PROFILER_STACK_SAMPLING_PROFILER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 
 namespace base {
 
 class NativeStackSampler;
+class NativeStackSamplerTestDelegate;
 
 // 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.
 //
 // Sample StackSamplingProfiler usage:
 //
 //   // Create and customize params as desired.
 //   base::StackStackSamplingProfiler::SamplingParams params;
@@ skipping 116 matching lines @@
   // The callback type used to collect completed profiles.
   //
   // IMPORTANT NOTE: the callback is invoked on a thread the profiler
   // constructs, rather than on the thread used to construct the profiler and
   // set the callback, and thus the callback must be callable on any thread. For
   // threads with message loops that create StackSamplingProfilers, posting a
   // task to the message loop with a copy of the profiles is the recommended
   // thread-safe callback implementation.
   using CompletedCallback = Callback<void(const CallStackProfiles&)>;
 
-  // Creates a profiler that sends completed profiles to |callback|.
+  // Creates a profiler that sends completed profiles to |callback|. The second
+  // constructor is for test purposes.

[brucedawson, 2015/10/30 00:15:59]

Wouldn't it be simpler to have test_delegate have a default value and just have
the one constructor?

[Mike Wittman, 2015/10/30 17:08:07]

I'm not sure. Although default arguments are permitted on constructors, using
separate functions is consistent with the rest of the code where they're
prohibited. This way probably looks less strange to the average reader who's
unfamiliar with the quirks of the style guide.

   StackSamplingProfiler(PlatformThreadId thread_id,
                         const SamplingParams& params,
                         const CompletedCallback& callback);
+  StackSamplingProfiler(PlatformThreadId thread_id,
+                        const SamplingParams& params,
+                        const CompletedCallback& callback,
+                        NativeStackSamplerTestDelegate* test_delegate);
   // 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);
 
@@ skipping 51 matching lines @@
   // The thread whose stack will be sampled.
   PlatformThreadId thread_id_;
 
   const SamplingParams params_;
 
   scoped_ptr<SamplingThread> sampling_thread_;
   PlatformThreadHandle sampling_thread_handle_;
 
   const CompletedCallback completed_callback_;
 
+  // Stored until it can be passed to the NativeStackSampler created in Start().
+  NativeStackSamplerTestDelegate* const test_delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
 };
 
 // The metrics provider code wants to put Samples in a map and compare them,
 // which requires us to define a few operators.
 BASE_EXPORT bool operator==(const StackSamplingProfiler::Frame& a,
                             const StackSamplingProfiler::Frame& b);
 BASE_EXPORT bool operator<(const StackSamplingProfiler::Frame& a,
                            const StackSamplingProfiler::Frame& b);
 
 }  // namespace base
 
 #endif  // BASE_PROFILER_STACK_SAMPLING_PROFILER_H_