Support "shared" histograms between processes.

components/metrics/metrics_service.cc

Index: components/metrics/metrics_service.cc
diff --git a/components/metrics/metrics_service.cc b/components/metrics/metrics_service.cc
index 55aa9f10c8c0daaf3e0a764020602c5e3d7c5d1b..e868ea7c9bb1cc087644257b65c44e3edcf9e346 100644
--- a/components/metrics/metrics_service.cc
+++ b/components/metrics/metrics_service.cc
@@ -251,6 +251,40 @@ SyntheticTrialGroup::SyntheticTrialGroup(uint32 trial, uint32 group) {
 SyntheticTrialGroup::~SyntheticTrialGroup() {
 }
 
+MetricsService::PersistentHistogramIterator::PersistentHistogramIterator(
+    AllocatorSet& allocators,
+    AllocatorSet::iterator pos)
+    : allocators_(allocators),
+      allocator_iter_(pos) {
+  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(
+          *allocator_iter_, &histogram_iter_);
+      if (h) {
+        current_histogram_ = new HistogramPointer(h);
+        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_);
+    }
+  }
+  return *this;
+}
+
 // static
 MetricsService::ShutdownCleanliness MetricsService::clean_shutdown_status_ =
     MetricsService::CLEANLY_SHUTDOWN;
@@ -547,6 +581,18 @@ void MetricsService::PushExternalLog(const std::string& log) {
   log_manager_.StoreLog(log, MetricsLog::ONGOING_LOG);
 }
 
+void MetricsService::AddPersistentMemorySegment(
+    base::PersistentMemoryAllocator* allocator) {
+  DCHECK(allocators_.find(allocator) == allocators_.end());
+  allocators_.insert(allocator);
+}
+
+void MetricsService::RemovePersistentMemorySegment(
+    base::PersistentMemoryAllocator* allocator) {
+  DCHECK(allocators_.find(allocator) != allocators_.end());
+  allocators_.erase(allocator);
+}
+
 //------------------------------------------------------------------------------
 // private methods
 //------------------------------------------------------------------------------
@@ -746,6 +792,11 @@ void MetricsService::CloseCurrentLog() {
     OpenNewLog();  // Start trivial log to hold our histograms.
   }
 
+  base::PersistentMemoryAllocator* allocator =
+      base::HistogramBase::GetDefaultPersistentMemoryAllocator();
+  if (allocator)
+    allocator->UpdateStaticHistograms();
+
   // Put incremental data (histogram deltas, and realtime stats deltas) at the
   // end of all log transmissions (initial log handles this separately).
   // RecordIncrementalStabilityElements only exists on the derived
@@ -1105,12 +1156,17 @@ void MetricsService::RecordCurrentEnvironment(MetricsLog* log) {
 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);
+  histogram_snapshot_manager_.PrepareDeltas(
+      persistent_begin(), persistent_end(),
       base::Histogram::kNoFlags, base::Histogram::kUmaTargetedHistogramFlag);
 }
 
 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);
 }
 
@@ -1149,4 +1205,12 @@ void MetricsService::SkipAndDiscardUpload() {
   log_upload_in_progress_ = false;
 }
 
+MetricsService::PersistentHistogramIterator MetricsService::persistent_begin() {
+  return PersistentHistogramIterator(allocators_, allocators_.begin());
+}
+
+MetricsService::PersistentHistogramIterator MetricsService::persistent_end() {
+  return PersistentHistogramIterator(allocators_, allocators_.end());
+}
+
 }  // namespace metrics