Support experiment configurations with/without stability metrics.

components/metrics/metrics_service.cc

 // Copyright 2014 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.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 896 matching lines @@
     SendStagedLog();
   }
   if (is_cellular_logic) {
     UMA_HISTOGRAM_BOOLEAN("UMA.LogUpload.Canceled.CellularConstraint",
                           upload_canceled);
   }
 }
 
 bool MetricsService::ProvidersHaveInitialStabilityMetrics() {
   // Check whether any metrics provider has initial stability metrics.
-  for (MetricsProvider* provider : metrics_providers_) {
-    if (provider->HasInitialStabilityMetrics())
-      return true;
-  }
+  bool has_stability_metrics = false;
+  for (MetricsProvider* provider : metrics_providers_)
+    has_stability_metrics |= provider->HasInitialStabilityMetrics();

[Alexei Svitkine (slow), 2016/11/24 21:27:58]

Please add a comment above why this doesn't do an early return.

[bcwhite, 2016/11/25 18:51:58]

Done.

 
-  return false;
+  return has_stability_metrics;
 }
 
 bool MetricsService::PrepareInitialStabilityLog(
     const std::string& prefs_previous_version) {
   DCHECK_EQ(INITIALIZED, state_);
 
   std::unique_ptr<MetricsLog> initial_stability_log(
       CreateLog(MetricsLog::INITIAL_STABILITY_LOG));
 
   // Do not call NotifyOnDidCreateMetricsLog here because the stability
@@ skipping 293 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics