043.patch

--- a/base/metrics/histogram.cc	2017-10-04 18:07:32.000000000 -0400
+++ b/base/metrics/histogram.cc	2017-10-08 20:06:49.944125362 -0400
@@ -124,7 +124,9 @@
       minimum_(minimum),
       maximum_(maximum),
       bucket_count_(bucket_count),
-      flags_(flags) {}
+      flags_(flags),
+      enabled_(HistogramBase::MetricsEnabled()) {}
+
 
   // Create a BucketRanges structure appropriate for this histogram.
   virtual BucketRanges* CreateRanges() {
@@ -154,13 +156,18 @@
   HistogramBase::Sample maximum_;
   uint32_t bucket_count_;
   int32_t flags_;
+  const bool enabled_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Factory);
 };
 
 HistogramBase* Histogram::Factory::Build() {
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name_);
+  std::string overridden_name = HistogramBase::kDummyName;
+  if (enabled_)
+    overridden_name = name_;
+
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(overridden_name);
   if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     const BucketRanges* created_ranges = CreateRanges();
@@ -191,7 +198,7 @@
     if (allocator) {
       tentative_histogram = allocator->AllocateHistogram(
           histogram_type_,
-          name_,
+          overridden_name,
           minimum_,
           maximum_,
           registered_ranges,
@@ -232,6 +239,10 @@
     ReportHistogramActivity(*histogram, HISTOGRAM_LOOKUP);
   }
 
+  if (!enabled_)
+    return histogram;
+
+  histogram->enabled = true;
   CHECK_EQ(histogram_type_, histogram->GetHistogramType()) << name_;
   if (bucket_count_ != 0 &&
       !histogram->HasConstructionArguments(minimum_, maximum_, bucket_count_)) {
@@ -468,10 +479,16 @@
 }
 
 void Histogram::Add(int value) {
+  if (!enabled)
+    return;
+
   AddCount(value, 1);
 }
 
 void Histogram::AddCount(int value, int count) {
+  if (!enabled)
+    return;
+
   DCHECK_EQ(0, ranges(0));
   DCHECK_EQ(kSampleType_MAX, ranges(bucket_count()));
 
@@ -526,10 +543,16 @@
 }
 
 void Histogram::AddSamples(const HistogramSamples& samples) {
+  if (!enabled)
+    return;
+
   unlogged_samples_->Add(samples);
 }
 
 bool Histogram::AddSamplesFromPickle(PickleIterator* iter) {
+  if (!enabled)
+    return true;
+
   return unlogged_samples_->AddFromPickle(iter);
 }