Support saving browser metrics to disk and reading them during next run.

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 1137 matching lines @@
     if ((*it)->flags() & base::Histogram::kUmaTargetedHistogramFlag)
       histogram_snapshot_manager_.PrepareDelta(*it);
   }
   for (MetricsProvider* provider : metrics_providers_)
     provider->RecordHistogramSnapshots(&histogram_snapshot_manager_);
   histogram_snapshot_manager_.FinishDeltas();
 }
 
 void MetricsService::RecordCurrentStabilityHistograms() {
   DCHECK(log_manager_.current_log());
+  histogram_snapshot_manager_.StartDeltas();
   // "true" indicates that StatisticsRecorder should include histograms in
   // persistent storage.
-  histogram_snapshot_manager_.PrepareDeltas(
-      base::StatisticsRecorder::begin(true), base::StatisticsRecorder::end(),
-      base::Histogram::kNoFlags, base::Histogram::kUmaStabilityHistogramFlag);
+  for (auto it = base::StatisticsRecorder::begin(true),
+            end = base::StatisticsRecorder::end();
+       it != end; ++it) {
+    // kUmaStabilityHistogramFlag is actually a combination of two flags and
+    // so the result of the bitwise-and must be checked against the "flag"
+    // value or incorrect matches will occur.
+    if (((*it)->flags() & base::Histogram::kUmaStabilityHistogramFlag) ==
+        base::Histogram::kUmaStabilityHistogramFlag) {
+      histogram_snapshot_manager_.PrepareDelta(*it);
+    }
+  }
+  for (MetricsProvider* provider : metrics_providers_)
+    provider->RecordInitialHistogramSnapshots(&histogram_snapshot_manager_);
+  histogram_snapshot_manager_.FinishDeltas();
 }
 
 void MetricsService::LogCleanShutdown() {
   // Redundant setting to assure that we always reset this value at shutdown
   // (and that we don't use some alternate path, and not call LogCleanShutdown).
   clean_shutdown_status_ = CLEANLY_SHUTDOWN;
 
   clean_exit_beacon_.WriteBeaconValue(true);
   RecordCurrentState(local_state_);
   local_state_->SetInteger(prefs::kStabilityExecutionPhase,
@@ skipping 18 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics