Make stack sampling profiler sample beyond startup.

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 <stddef.h>
 
 #include <memory>
@@ skipping 197 matching lines @@
     // was started between when the idle-shutdown was initiated and when it
     // runs.
     static void PerformSamplingThreadIdleShutdown(
         bool simulate_intervening_start);
   };
 
   // The callback type used to collect completed profiles. The passed |profiles|
   // are move-only. Other threads, including the UI thread, may block on
   // callback completion so this should run as quickly as possible.
   //
+  // After collection completion, the callback may instruct the profiler to do
+  // additional collection(s) by modifying the SamplingParams argument and
+  // returning true to indicate collection should be started again.
+  //
   // 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 the moved (i.e. std::move) profiles is the
   // thread-safe callback implementation.
-  using CompletedCallback = Callback<void(CallStackProfiles)>;
+  using CompletedCallback = Callback<bool(CallStackProfiles, SamplingParams*)>;
 
   // Creates a profiler for the CURRENT thread that sends completed profiles
   // to |callback|. An optional |test_delegate| can be supplied by tests.
   // The caller must ensure that this object gets destroyed before the current
   // thread exits.
   StackSamplingProfiler(
       const SamplingParams& params,
       const CompletedCallback& callback,
       NativeStackSamplerTestDelegate* test_delegate = nullptr);
 
@@ skipping 85 matching lines @@
 BASE_EXPORT bool operator<(const StackSamplingProfiler::Sample& a,
                            const StackSamplingProfiler::Sample& b);
 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_