Support "shared" histograms between processes.

base/metrics/histogram_snapshot_manager.cc

Index: base/metrics/histogram_snapshot_manager.cc
diff --git a/base/metrics/histogram_snapshot_manager.cc b/base/metrics/histogram_snapshot_manager.cc
index 0b3e9a4550c978c37852a7c2dd5e3539e7f38c14..ef1ab26284b4e20852acfe7a278446af7943fdea 100644
--- a/base/metrics/histogram_snapshot_manager.cc
+++ b/base/metrics/histogram_snapshot_manager.cc
@@ -22,27 +22,13 @@ HistogramSnapshotManager::~HistogramSnapshotManager() {
   STLDeleteValues(&logged_samples_);
 }
 
-void HistogramSnapshotManager::PrepareDeltas(
-    HistogramBase::Flags flag_to_set,
-    HistogramBase::Flags required_flags) {
-  StatisticsRecorder::Histograms histograms;
-  StatisticsRecorder::GetHistograms(&histograms);
-  for (StatisticsRecorder::Histograms::const_iterator it = histograms.begin();
-       histograms.end() != it;
-       ++it) {
-    (*it)->SetFlags(flag_to_set);
-    if (((*it)->flags() & required_flags) == required_flags)
-      PrepareDelta(**it);
-  }
-}
-
 void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
   DCHECK(histogram_flattener_);
 
   // Get up-to-date snapshot of sample stats.
   scoped_ptr<HistogramSamples> snapshot(histogram.SnapshotSamples());
   const std::string& histogram_name = histogram.histogram_name();
-  const uint64_t histogram_id = histogram.name_hash();
+  const uint64_t histogram_hash = histogram.name_hash();
 
   int corruption = histogram.FindCorruption(*snapshot);
 
@@ -66,10 +52,10 @@ void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
     histogram_flattener_->InconsistencyDetected(
         static_cast<HistogramBase::Inconsistency>(corruption));
     // Don't record corrupt data to metrics services.
-    int old_corruption = inconsistencies_[histogram_id];
+    int old_corruption = inconsistencies_[histogram_hash];
     if (old_corruption == (corruption | old_corruption))
       return;  // We've already seen this corruption for this histogram.
-    inconsistencies_[histogram_id] |= corruption;
+    inconsistencies_[histogram_hash] |= corruption;
     histogram_flattener_->UniqueInconsistencyDetected(
         static_cast<HistogramBase::Inconsistency>(corruption));
     return;
@@ -77,12 +63,12 @@ void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
 
   HistogramSamples* to_log;
   std::map<uint64_t, HistogramSamples*>::iterator it =
-      logged_samples_.find(histogram_id);
+      logged_samples_.find(histogram_hash);
   if (it == logged_samples_.end()) {
     to_log = snapshot.release();
 
     // This histogram has not been logged before, add a new entry.
-    logged_samples_[histogram_id] = to_log;
+    logged_samples_[histogram_hash] = to_log;
   } else {
     HistogramSamples* already_logged = it->second;
     InspectLoggedSamplesInconsistency(*snapshot, already_logged);