Make stack sampling profiler sample beyond startup.

components/metrics/child_call_stack_profile_collector.cc

 // 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.
 
 #include "components/metrics/child_call_stack_profile_collector.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 47 matching lines @@
   parent_collector_ = std::move(parent_collector);
   if (parent_collector_) {
     for (ProfilesState& state : profiles_) {
       parent_collector_->Collect(state.params, state.start_timestamp,
                                  std::move(state.profiles));
     }
   }
   profiles_.clear();
 }
 
-void ChildCallStackProfileCollector::Collect(
+base::Optional<base::StackSamplingProfiler::SamplingParams>
+ChildCallStackProfileCollector::Collect(
     const CallStackProfileParams& params,
     base::TimeTicks start_timestamp,
     std::vector<CallStackProfile> profiles) {
+  // Impl function is used as it needs to PostTask() to itself on a different
+  // thread - which only works with a void return value.
+  CollectImpl(params, start_timestamp, std::move(profiles));
+  // Empty return value indicates that collection should not be re-started.
+  return base::Optional<base::StackSamplingProfiler::SamplingParams>();
+}
+
+void ChildCallStackProfileCollector::CollectImpl(
+    const CallStackProfileParams& params,
+    base::TimeTicks start_timestamp,
+    std::vector<CallStackProfile> profiles) {
   base::AutoLock alock(lock_);
   if (task_runner_ &&
       // The profiler thread does not have a task runner. Attempting to
       // invoke Get() on it results in a DCHECK.
       (!base::ThreadTaskRunnerHandle::IsSet() ||
        base::ThreadTaskRunnerHandle::Get() != task_runner_)) {
     // Post back to the thread that owns the the parent interface.
-    task_runner_->PostTask(FROM_HERE, base::Bind(
-        &ChildCallStackProfileCollector::Collect,
-        // This class has lazy instance lifetime.
-        base::Unretained(this),
-        params,
-        start_timestamp,
-        base::Passed(std::move(profiles))));
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&ChildCallStackProfileCollector::CollectImpl,
+                              // This class has lazy instance lifetime.
+                              base::Unretained(this), params, start_timestamp,
+                              base::Passed(std::move(profiles))));
     return;
   }
 
   if (parent_collector_) {
     parent_collector_->Collect(params, start_timestamp, std::move(profiles));
   } else if (retain_profiles_) {
     profiles_.push_back(
         ProfilesState(params, start_timestamp, std::move(profiles)));
   }
 }
 
 }  // namespace metrics