Merge multiple histogram snapshots into single one for reporting.

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 234 matching lines @@
 
 SyntheticTrialGroup::SyntheticTrialGroup(uint32 trial, uint32 group) {
   id.name = trial;
   id.group = group;
 }
 
 SyntheticTrialGroup::~SyntheticTrialGroup() {
 }
 
 MetricsService::PersistentHistogramIterator::PersistentHistogramIterator(
+    HistogramSet* found_histograms,
     AllocatorSet& allocators,
     AllocatorSet::iterator pos)
     : allocators_(allocators),
-      allocator_iter_(pos) {
+      allocator_iter_(pos),
+      found_histograms_(found_histograms) {
   if (pos != allocators_.end()) {
     (*allocator_iter_)->CreateIterator(&histogram_iter_);
     // Have to call ++ to advance iterator to the first persistent histogram.
     operator++();
   }
 }
 
 MetricsService::PersistentHistogramIterator&
 MetricsService::PersistentHistogramIterator::operator++() {
   if (allocator_iter_ != allocators_.end()) {
     for (;;) {
-      base::HistogramBase* h = base::HistogramBase::GetNextPersistentHistogram(
+      current_histogram_ = base::HistogramBase::GetNextPersistentHistogram(
           *allocator_iter_, &histogram_iter_);
-      if (h) {
-        current_histogram_ = new HistogramPointer(h);
+      if (current_histogram_) {
+        DCHECK(found_histograms_->find(current_histogram_) ==
+               found_histograms_->end());
+        found_histograms_->insert(current_histogram_);
         break;
       }
       allocator_iter_++;
       if (allocator_iter_ == allocators_.end()) {
         histogram_iter_.clear();  // Clear so it matches end() iterator.
         current_histogram_ = nullptr;
         break;
       }
       (*allocator_iter_)->CreateIterator(&histogram_iter_);
     }
@@ skipping 867 matching lines @@
   GetSyntheticFieldTrialsOlderThan(log->creation_time(), &synthetic_trials);
   log->RecordEnvironment(metrics_providers_.get(), synthetic_trials,
                          GetInstallDate(), GetMetricsReportingEnabledDate());
 }
 
 void MetricsService::RecordCurrentHistograms() {
   DCHECK(log_manager_.current_log());
   histogram_snapshot_manager_.PrepareDeltas(
       base::StatisticsRecorder::begin(true), base::StatisticsRecorder::end(),
       base::Histogram::kNoFlags, base::Histogram::kUmaTargetedHistogramFlag);
+  HistogramSet persistent_histograms;
   histogram_snapshot_manager_.PrepareDeltas(
-      persistent_begin(), persistent_end(),
+      persistent_begin(&persistent_histograms), persistent_end(),
       base::Histogram::kNoFlags, base::Histogram::kUmaTargetedHistogramFlag);
+  STLDeleteElements(&persistent_histograms);
 }
 
 void MetricsService::RecordCurrentStabilityHistograms() {
   DCHECK(log_manager_.current_log());
   histogram_snapshot_manager_.PrepareDeltas(
       base::StatisticsRecorder::begin(true), base::StatisticsRecorder::end(),
       base::Histogram::kNoFlags, base::Histogram::kUmaStabilityHistogramFlag);
 }
 
 void MetricsService::LogCleanShutdown() {
@@ skipping 24 matching lines @@
   pref->SetInt64(prefs::kStabilityLastTimestampSec,
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
-MetricsService::PersistentHistogramIterator MetricsService::persistent_begin() {
-  return PersistentHistogramIterator(allocators_, allocators_.begin());
+MetricsService::PersistentHistogramIterator MetricsService::persistent_begin(
+    HistogramSet* found) {
+  return PersistentHistogramIterator(found, allocators_, allocators_.begin());
 }
 
 MetricsService::PersistentHistogramIterator MetricsService::persistent_end() {
-  return PersistentHistogramIterator(allocators_, allocators_.end());
+  return PersistentHistogramIterator(nullptr, allocators_, allocators_.end());
 }
 
 }  // namespace metrics