Make stack sampling profiler sample beyond startup.

components/metrics/child_call_stack_profile_collector.h

 // Copyright 2016 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 COMPONENTS_METRICS_CHILD_CALL_STACK_PROFILE_COLLECTOR_H_
 #define COMPONENTS_METRICS_CHILD_CALL_STACK_PROFILE_COLLECTOR_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 72 matching lines @@
 
     // The sampled profiles.
     base::StackSamplingProfiler::CallStackProfiles profiles;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ProfilesState);
   };
 
   using CallStackProfile = base::StackSamplingProfiler::CallStackProfile;
 
-  void Collect(const CallStackProfileParams& params,
-               base::TimeTicks start_timestamp,
-               std::vector<CallStackProfile> profiles);
+  base::Optional<base::StackSamplingProfiler::SamplingParams> Collect(
+      const CallStackProfileParams& params,
+      base::TimeTicks start_timestamp,
+      std::vector<CallStackProfile> profiles);
+
+  void CollectImpl(const CallStackProfileParams& params,
+                   base::TimeTicks start_timestamp,
+                   std::vector<CallStackProfile> profiles);
 
   // This object may be accessed on any thread, including the profiler
   // thread. The expected use case for the object is to be created and have
   // GetProfilerCallback before the message loop starts, which prevents the use
   // of PostTask and the like for inter-thread communication.
   base::Lock lock_;
 
   // Whether to retain profiles when the interface is not set. Remains true
   // until the invocation of SetParentProfileCollector(), at which point it is
   // false for the rest of the object lifetime.
@@ skipping 11 matching lines @@
   // Profiles being cached by this object, pending a parent interface to be
   // supplied.
   std::vector<ProfilesState> profiles_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildCallStackProfileCollector);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_CHILD_CALL_STACK_PROFILE_COLLECTOR_H_