Support "shared" histograms between processes.

base/metrics/histogram.cc

 // Copyright (c) 2012 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.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 // See header file for details and examples.
 
 #include "base/metrics/histogram.h"
 
 #include <limits.h>
 #include <math.h>
 
 #include <algorithm>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/histogram_persistence.h"
 #include "base/metrics/metrics_hashes.h"
+#include "base/metrics/persistent_memory_allocator.h"
 #include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
 #include "base/values.h"
 
 namespace base {
 
@@ skipping 44 matching lines @@
 }
 
 }  // namespace
 
 typedef HistogramBase::Count Count;
 typedef HistogramBase::Sample Sample;
 
 // static
 const size_t Histogram::kBucketCount_MAX = 16384u;
 
+class Histogram::Factory {
+ public:
+  Factory(const std::string& name,
+          HistogramBase::Sample minimum,
+          HistogramBase::Sample maximum,
+          size_t bucket_count,
+          int32_t flags)
+    : Factory(name, HISTOGRAM, minimum, maximum, bucket_count, flags) {}
+
+  HistogramBase* Build();

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

Can this have a comment? Specifically also mentioning the ownership of the
return value.

[bcwhite, 2016/01/14 19:20:25]

Done.

+
+ protected:
+  Factory(const std::string& name,
+          HistogramType histogram_type,
+          HistogramBase::Sample minimum,
+          HistogramBase::Sample maximum,
+          size_t bucket_count,
+          int32_t flags)
+    : name_(name),
+      histogram_type_(histogram_type),
+      minimum_(minimum),
+      maximum_(maximum),
+      bucket_count_(bucket_count),
+      flags_(flags) {}
+
+  // Create a BucketRanges structure appropriate for this histogram.
+  virtual BucketRanges* CreateRanges() {
+    BucketRanges* ranges = new BucketRanges(bucket_count_ + 1);
+    Histogram::InitializeBucketRanges(minimum_, maximum_, ranges);
+    return ranges;
+  }
+
+  // Allocate the correct Histogram object off the heap (in case persistent
+  // memory is not available).
+  virtual HistogramBase* HeapAlloc(const BucketRanges* ranges) {
+    return new Histogram(name_, minimum_, maximum_, ranges);
+  }
+
+  // Perform any required datafill on the just-created histogram.  If
+  // overridden, be sure to call the "super" version.
+  virtual void FillHistogram(HistogramBase* histogram) {
+    histogram->SetFlags(flags_);
+  }
+
+  // These values are protected (instead of private) because they need to
+  // be accessible to methods of sub-classes in order to avoid passing
+  // unnecessary parameters everywhere.
+  const std::string& name_;
+  const HistogramType histogram_type_;
+  HistogramBase::Sample minimum_;
+  HistogramBase::Sample maximum_;
+  size_t bucket_count_;
+  int32_t flags_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Factory);
+};
+
+HistogramBase* Histogram::Factory::Build() {
+  ImportPersistentHistograms();

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

I don't understand this call. Is it needed? If so, please add an explanation
comment.

[bcwhite, 2016/01/14 19:20:25]

Done.

+
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name_);
+  if (!histogram) {

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

Prefer an early return if found, so the rest of the code doesn't need to be
indented.

[bcwhite, 2016/01/14 19:20:25]

Found doesn't mean it's correct.  There are additional checks at the bottom of
the method to ensure that the histogram being requested matches the one that is
known.

This existed in previous code, presumably to ensure that the results are
identical should the same histogram be instantiated via macros at different
places in the code.

[Alexei Svitkine (slow), 2016/01/14 21:53:41]

Ok, that's fair. Let's keep as-is then.

+    // To avoid racy destruction at shutdown, the following will be leaked.
+    const BucketRanges* created_ranges = CreateRanges();
+    const BucketRanges* registered_ranges =
+        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(created_ranges);
+
+    // Sometimes the bucket info is dynamically determined in CreateRanges().

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

Can this comment have more context? When exactly is this the case?

[bcwhite, 2016/01/14 19:20:25]

Done.

+    if (bucket_count_ == 0) {
+      bucket_count_ = registered_ranges->bucket_count();
+      minimum_ = registered_ranges->range(1);
+      maximum_ = registered_ranges->range(bucket_count_ - 1);
+    }
+
+    PersistentMemoryAllocator::Reference histogram_ref = 0;
+    HistogramBase* tentative_histogram = nullptr;
+    PersistentMemoryAllocator* allocator =
+        GetPersistentHistogramMemoryAllocator();

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

Add a comment above this that mentions that currently the presence of the
allocator is controlled by an base::Feature that's off by default. And that if
one doesn't exist, this allocates the histograms on the heap.

[bcwhite, 2016/01/14 19:20:25]

Done.

+    if (allocator) {
+      flags_ |= HistogramBase::kIsPersistent;
+      tentative_histogram = AllocatePersistentHistogram(
+          allocator,
+          histogram_type_,
+          name_,
+          minimum_,
+          maximum_,
+          registered_ranges,
+          flags_,
+          &histogram_ref);
+    }
+
+    // Handle the case where no persistent allocator is present or the
+    // persistent allocation fails (perhaps because it is full).
+    if (!tentative_histogram) {
+      DCHECK(!histogram_ref);  // Should never have been set.
+      DCHECK(!allocator);  // Shouldn't have failed.
+      flags_ &= ~HistogramBase::kIsPersistent;
+      tentative_histogram = HeapAlloc(registered_ranges);
+    }
+
+    FillHistogram(tentative_histogram);
+    histogram =
+        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
+
+    // Persistent histograms need some follow-up processing.
+    if (histogram_ref) {
+      FinalizePersistentHistogram(histogram_ref,
+                                  histogram == tentative_histogram);
+    }
+  }
+
+  DCHECK_EQ(histogram_type_, histogram->GetHistogramType());
+  if (bucket_count_ != 0 &&
+      !histogram->HasConstructionArguments(minimum_, maximum_, bucket_count_)) {
+    // The construction arguments do not match the existing histogram.  This can
+    // come about if an extension updates in the middle of a chrome run and has
+    // changed one of them, or simply by bad code within Chrome itself.  We
+    // return NULL here with the expectation that bad code in Chrome will crash
+    // on dereference, but extension/Pepper APIs will guard against NULL and not
+    // crash.
+    DLOG(ERROR) << "Histogram " << name_ << " has bad construction arguments";
+    return nullptr;
+  }
+  return histogram;
+}
+

[Alexei Svitkine (slow), 2016/01/14 16:43:13]

Nit: Remove empty line.

[bcwhite, 2016/01/14 19:20:25]

Done.

+
 HistogramBase* Histogram::FactoryGet(const std::string& name,
                                      Sample minimum,
                                      Sample maximum,
                                      size_t bucket_count,
                                      int32_t flags) {
   bool valid_arguments =
       InspectConstructionArguments(name, &minimum, &maximum, &bucket_count);
   DCHECK(valid_arguments);
 
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
-  if (!histogram) {
-    // To avoid racy destruction at shutdown, the following will be leaked.
-    BucketRanges* ranges = new BucketRanges(bucket_count + 1);
-    InitializeBucketRanges(minimum, maximum, ranges);
-    const BucketRanges* registered_ranges =
-        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
-
-    Histogram* tentative_histogram =
-        new Histogram(name, minimum, maximum, registered_ranges);
-
-    tentative_histogram->SetFlags(flags);
-    histogram =
-        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
-  }
-
-  DCHECK_EQ(HISTOGRAM, histogram->GetHistogramType());
-  if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
-    // The construction arguments do not match the existing histogram.  This can
-    // come about if an extension updates in the middle of a chrome run and has
-    // changed one of them, or simply by bad code within Chrome itself.  We
-    // return NULL here with the expectation that bad code in Chrome will crash
-    // on dereference, but extension/Pepper APIs will guard against NULL and not
-    // crash.
-    DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
-    return NULL;
-  }
-  return histogram;
+  return Factory(name, minimum, maximum, bucket_count, flags).Build();
 }
 
 HistogramBase* Histogram::FactoryTimeGet(const std::string& name,
                                          TimeDelta minimum,
                                          TimeDelta maximum,
                                          size_t bucket_count,
                                          int32_t flags) {
   return FactoryGet(name, static_cast<Sample>(minimum.InMilliseconds()),
                     static_cast<Sample>(maximum.InMilliseconds()), bucket_count,
                     flags);
 }
 
 HistogramBase* Histogram::FactoryGet(const char* name,
                                      Sample minimum,
                                      Sample maximum,
                                      size_t bucket_count,
                                      int32_t flags) {
   return FactoryGet(std::string(name), minimum, maximum, bucket_count, flags);
 }
 
 HistogramBase* Histogram::FactoryTimeGet(const char* name,
                                          TimeDelta minimum,
                                          TimeDelta maximum,
                                          size_t bucket_count,
                                          int32_t flags) {
   return FactoryTimeGet(std::string(name), minimum, maximum, bucket_count,
                         flags);
 }
 
+HistogramBase* Histogram::PersistentGet(const char* name,
+                                        Sample minimum,
+                                        Sample maximum,
+                                        const BucketRanges* ranges,
+                                        HistogramBase::AtomicCount* counts,
+                                        size_t counts_size,
+                                        HistogramSamples::Metadata* meta) {
+  return new Histogram(name, minimum, maximum, ranges, counts, counts_size,
+                       meta);
+}
+
 // Calculate what range of values are held in each bucket.
 // We have to be careful that we don't pick a ratio between starting points in
 // consecutive buckets that is sooo small, that the integer bounds are the same
 // (effectively making one bucket get no values).  We need to avoid:
 //   ranges(i) == ranges(i + 1)
 // To avoid that, we just do a fine-grained bucket width as far as we need to
 // until we get a ratio that moves us along at least 2 units at a time.  From
 // that bucket onward we do use the exponential growth of buckets.
 //
 // static
@@ skipping 174 matching lines @@
                      Sample maximum,
                      const BucketRanges* ranges)
   : HistogramBase(name),
     bucket_ranges_(ranges),
     declared_min_(minimum),
     declared_max_(maximum) {
   if (ranges)
     samples_.reset(new SampleVector(HashMetricName(name), ranges));
 }
 
+Histogram::Histogram(const std::string& name,
+                     Sample minimum,
+                     Sample maximum,
+                     const BucketRanges* ranges,
+                     HistogramBase::AtomicCount* counts,
+                     size_t counts_size,
+                     HistogramSamples::Metadata* meta)
+  : HistogramBase(name),
+    bucket_ranges_(ranges),
+    declared_min_(minimum),
+    declared_max_(maximum) {
+  if (ranges) {
+    samples_.reset(new SampleVector(HashMetricName(name),
+                                    counts, counts_size, meta, ranges));
+  }
+}
+
 Histogram::~Histogram() {
 }
 
 bool Histogram::PrintEmptyBucket(size_t index) const {
   return true;
 }
 
 // Use the actual bucket widths (like a linear histogram) until the widths get
 // over some transition value, and then use that transition width.  Exponentials
 // get so big so fast (and we don't expect to see a lot of entries in the large
@@ skipping 181 matching lines @@
       ++index;
     }
   }
 }
 
 //------------------------------------------------------------------------------
 // LinearHistogram: This histogram uses a traditional set of evenly spaced
 // buckets.
 //------------------------------------------------------------------------------
 
+class LinearHistogram::Factory : public Histogram::Factory {
+ public:
+  Factory(const std::string& name,
+          HistogramBase::Sample minimum,
+          HistogramBase::Sample maximum,
+          size_t bucket_count,
+          int32_t flags,
+          const DescriptionPair* descriptions)
+    : Histogram::Factory(name, LINEAR_HISTOGRAM, minimum, maximum,
+                         bucket_count, flags) {
+    descriptions_ = descriptions;
+  }
+
+ protected:
+  BucketRanges* CreateRanges() override {
+    BucketRanges* ranges = new BucketRanges(bucket_count_ + 1);
+    LinearHistogram::InitializeBucketRanges(minimum_, maximum_, ranges);
+    return ranges;
+  }
+
+  HistogramBase* HeapAlloc(const BucketRanges* ranges) override {
+    return new LinearHistogram(name_, minimum_, maximum_, ranges);
+  }
+
+  void FillHistogram(HistogramBase* base_histogram) override {
+    Histogram::Factory::FillHistogram(base_histogram);
+    LinearHistogram* histogram = static_cast<LinearHistogram*>(base_histogram);
+    // Set range descriptions.
+    if (descriptions_) {
+      for (int i = 0; descriptions_[i].description; ++i) {
+        histogram->bucket_description_[descriptions_[i].sample] =
+            descriptions_[i].description;
+      }
+    }
+  }
+
+ private:
+  const DescriptionPair* descriptions_;
+
+  DISALLOW_COPY_AND_ASSIGN(Factory);
+};
+
 LinearHistogram::~LinearHistogram() {}
 
 HistogramBase* LinearHistogram::FactoryGet(const std::string& name,
                                            Sample minimum,
                                            Sample maximum,
                                            size_t bucket_count,
                                            int32_t flags) {
   return FactoryGetWithRangeDescription(
       name, minimum, maximum, bucket_count, flags, NULL);
 }
@@ skipping 18 matching lines @@
 
 HistogramBase* LinearHistogram::FactoryTimeGet(const char* name,
                                                TimeDelta minimum,
                                                TimeDelta maximum,
                                                size_t bucket_count,
                                                int32_t flags) {
   return FactoryTimeGet(std::string(name),  minimum, maximum, bucket_count,
                         flags);
 }
 
+HistogramBase* LinearHistogram::PersistentGet(
+    const char* name,
+    Sample minimum,
+    Sample maximum,
+    const BucketRanges* ranges,
+    HistogramBase::AtomicCount* counts,
+    size_t counts_size,
+    HistogramSamples::Metadata* meta) {
+  return new LinearHistogram(name, minimum, maximum, ranges, counts,
+                             counts_size, meta);
+}
+
 HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
     const std::string& name,
     Sample minimum,
     Sample maximum,
     size_t bucket_count,
     int32_t flags,
     const DescriptionPair descriptions[]) {
   bool valid_arguments = Histogram::InspectConstructionArguments(
       name, &minimum, &maximum, &bucket_count);
   DCHECK(valid_arguments);
 
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
-  if (!histogram) {
-    // To avoid racy destruction at shutdown, the following will be leaked.
-    BucketRanges* ranges = new BucketRanges(bucket_count + 1);
-    InitializeBucketRanges(minimum, maximum, ranges);
-    const BucketRanges* registered_ranges =
-        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
-
-    LinearHistogram* tentative_histogram =
-        new LinearHistogram(name, minimum, maximum, registered_ranges);
-
-    // Set range descriptions.
-    if (descriptions) {
-      for (int i = 0; descriptions[i].description; ++i) {
-        tentative_histogram->bucket_description_[descriptions[i].sample] =
-            descriptions[i].description;
-      }
-    }
-
-    tentative_histogram->SetFlags(flags);
-    histogram =
-        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
-  }
-
-  DCHECK_EQ(LINEAR_HISTOGRAM, histogram->GetHistogramType());
-  if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
-    // The construction arguments do not match the existing histogram.  This can
-    // come about if an extension updates in the middle of a chrome run and has
-    // changed one of them, or simply by bad code within Chrome itself.  We
-    // return NULL here with the expectation that bad code in Chrome will crash
-    // on dereference, but extension/Pepper APIs will guard against NULL and not
-    // crash.
-    DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
-    return NULL;
-  }
-  return histogram;
+  return Factory(name, minimum, maximum, bucket_count, flags, descriptions)
+      .Build();
 }
 
 HistogramType LinearHistogram::GetHistogramType() const {
   return LINEAR_HISTOGRAM;
 }
 
 LinearHistogram::LinearHistogram(const std::string& name,
                                  Sample minimum,
                                  Sample maximum,
                                  const BucketRanges* ranges)
     : Histogram(name, minimum, maximum, ranges) {
 }
 
+LinearHistogram::LinearHistogram(const std::string& name,
+                                 Sample minimum,
+                                 Sample maximum,
+                                 const BucketRanges* ranges,
+                                 HistogramBase::AtomicCount* counts,
+                                 size_t counts_size,
+                                 HistogramSamples::Metadata* meta)
+    : Histogram(name,
+                minimum,
+                maximum,
+                ranges,
+                counts,
+                counts_size,
+                meta) {}
+
 double LinearHistogram::GetBucketSize(Count current, size_t i) const {
   DCHECK_GT(ranges(i + 1), ranges(i));
   // Adjacent buckets with different widths would have "surprisingly" many (few)
   // samples in a histogram if we didn't normalize this way.
   double denominator = ranges(i + 1) - ranges(i);
   return current/denominator;
 }
 
 const std::string LinearHistogram::GetAsciiBucketRange(size_t i) const {
   int range = ranges(i);
@@ skipping 43 matching lines @@
     // The serialized histogram might be corrupted.
     return NULL;
   }
   return histogram;
 }
 
 //------------------------------------------------------------------------------
 // This section provides implementation for BooleanHistogram.
 //------------------------------------------------------------------------------
 
+class BooleanHistogram::Factory : public Histogram::Factory {
+ public:
+  Factory(const std::string& name, int32_t flags)
+    : Histogram::Factory(name, BOOLEAN_HISTOGRAM, 1, 2, 3, flags) {}
+
+ protected:
+  BucketRanges* CreateRanges() {
+    BucketRanges* ranges = new BucketRanges(3 + 1);
+    LinearHistogram::InitializeBucketRanges(1, 2, ranges);
+    return ranges;
+  }
+
+  HistogramBase* HeapAlloc(const BucketRanges* ranges) override {
+    return new BooleanHistogram(name_, ranges);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Factory);
+};
+
 HistogramBase* BooleanHistogram::FactoryGet(const std::string& name,
                                             int32_t flags) {
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
-  if (!histogram) {
-    // To avoid racy destruction at shutdown, the following will be leaked.
-    BucketRanges* ranges = new BucketRanges(4);
-    LinearHistogram::InitializeBucketRanges(1, 2, ranges);
-    const BucketRanges* registered_ranges =
-        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
-
-    BooleanHistogram* tentative_histogram =
-        new BooleanHistogram(name, registered_ranges);
-
-    tentative_histogram->SetFlags(flags);
-    histogram =
-        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
-  }
-
-  DCHECK_EQ(BOOLEAN_HISTOGRAM, histogram->GetHistogramType());
-  return histogram;
+  return Factory(name, flags).Build();
 }
 
 HistogramBase* BooleanHistogram::FactoryGet(const char* name, int32_t flags) {
   return FactoryGet(std::string(name), flags);
 }
 
+HistogramBase* BooleanHistogram::PersistentGet(
+    const char* name,
+    const BucketRanges* ranges,
+    HistogramBase::AtomicCount* counts,
+    HistogramSamples::Metadata* meta) {
+  return new BooleanHistogram(name, ranges, counts, meta);
+}
+
 HistogramType BooleanHistogram::GetHistogramType() const {
   return BOOLEAN_HISTOGRAM;
 }
 
 BooleanHistogram::BooleanHistogram(const std::string& name,
                                    const BucketRanges* ranges)
     : LinearHistogram(name, 1, 2, ranges) {}
 
+BooleanHistogram::BooleanHistogram(const std::string& name,
+                                   const BucketRanges* ranges,
+                                   HistogramBase::AtomicCount* counts,
+                                   HistogramSamples::Metadata* meta)
+    : LinearHistogram(name, 1, 2, ranges, counts, 2, meta) {}
+
 HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
   std::string histogram_name;
   int flags;
   int declared_min;
   int declared_max;
   size_t bucket_count;
   uint32_t range_checksum;
 
   if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
                               &declared_max, &bucket_count, &range_checksum)) {
     return NULL;
   }
 
   HistogramBase* histogram = BooleanHistogram::FactoryGet(
       histogram_name, flags);
   if (!ValidateRangeChecksum(*histogram, range_checksum)) {
     // The serialized histogram might be corrupted.
     return NULL;
   }
   return histogram;
 }
 
 //------------------------------------------------------------------------------
 // CustomHistogram:
 //------------------------------------------------------------------------------
 
+class CustomHistogram::Factory : public Histogram::Factory {
+ public:
+  Factory(const std::string& name,
+          const std::vector<Sample>* custom_ranges,
+          int32_t flags)
+    : Histogram::Factory(name, CUSTOM_HISTOGRAM, 0, 0, 0, flags) {
+    custom_ranges_ = custom_ranges;
+  }
+
+ protected:
+  BucketRanges* CreateRanges() {
+    // Remove the duplicates in the custom ranges array.
+    std::vector<int> ranges = *custom_ranges_;
+    ranges.push_back(0);  // Ensure we have a zero value.
+    ranges.push_back(HistogramBase::kSampleType_MAX);
+    std::sort(ranges.begin(), ranges.end());
+    ranges.erase(std::unique(ranges.begin(), ranges.end()), ranges.end());
+
+    BucketRanges* bucket_ranges = new BucketRanges(ranges.size());
+    for (size_t i = 0; i < ranges.size(); i++) {
+      bucket_ranges->set_range(i, ranges[i]);
+    }
+    bucket_ranges->ResetChecksum();
+    return bucket_ranges;
+  }
+
+  HistogramBase* HeapAlloc(const BucketRanges* ranges) override {
+    return new CustomHistogram(name_, ranges);
+  }
+
+ private:
+  const std::vector<Sample>* custom_ranges_;
+
+  DISALLOW_COPY_AND_ASSIGN(Factory);
+};
+
 HistogramBase* CustomHistogram::FactoryGet(
     const std::string& name,
     const std::vector<Sample>& custom_ranges,
     int32_t flags) {
   CHECK(ValidateCustomRanges(custom_ranges));
 
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
-  if (!histogram) {
-    BucketRanges* ranges = CreateBucketRangesFromCustomRanges(custom_ranges);
-    const BucketRanges* registered_ranges =
-        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
-
-    // To avoid racy destruction at shutdown, the following will be leaked.
-    CustomHistogram* tentative_histogram =
-        new CustomHistogram(name, registered_ranges);
-
-    tentative_histogram->SetFlags(flags);
-
-    histogram =
-        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
-  }
-
-  DCHECK_EQ(histogram->GetHistogramType(), CUSTOM_HISTOGRAM);
-  return histogram;
+  return Factory(name, &custom_ranges, flags).Build();
 }
 
 HistogramBase* CustomHistogram::FactoryGet(
     const char* name,
     const std::vector<Sample>& custom_ranges,
     int32_t flags) {
   return FactoryGet(std::string(name), custom_ranges, flags);
 }
 
+HistogramBase* CustomHistogram::PersistentGet(
+    const char* name,
+    const BucketRanges* ranges,
+    HistogramBase::AtomicCount* counts,
+    size_t counts_size,
+    HistogramSamples::Metadata* meta) {
+  return new CustomHistogram(name, ranges, counts, counts_size, meta);
+}
+
 HistogramType CustomHistogram::GetHistogramType() const {
   return CUSTOM_HISTOGRAM;
 }
 
 // static
 std::vector<Sample> CustomHistogram::ArrayToCustomRanges(
     const Sample* values, size_t num_values) {
   std::vector<Sample> all_values;
   for (size_t i = 0; i < num_values; ++i) {
     Sample value = values[i];
     all_values.push_back(value);
 
     // Ensure that a guard bucket is added. If we end up with duplicate
     // values, FactoryGet will take care of removing them.
     all_values.push_back(value + 1);
   }
   return all_values;
 }
 
 CustomHistogram::CustomHistogram(const std::string& name,
                                  const BucketRanges* ranges)
     : Histogram(name,
                 ranges->range(1),
                 ranges->range(ranges->bucket_count() - 1),
                 ranges) {}
 
+CustomHistogram::CustomHistogram(const std::string& name,
+                                 const BucketRanges* ranges,
+                                 HistogramBase::AtomicCount* counts,
+                                 size_t counts_size,
+                                 HistogramSamples::Metadata* meta)
+    : Histogram(name,
+                ranges->range(1),
+                ranges->range(ranges->bucket_count() - 1),
+                ranges,
+                counts,
+                counts_size,
+                meta) {}
+
 bool CustomHistogram::SerializeInfoImpl(Pickle* pickle) const {
   if (!Histogram::SerializeInfoImpl(pickle))
     return false;
 
   // Serialize ranges. First and last ranges are alwasy 0 and INT_MAX, so don't
   // write them.
   for (size_t i = 1; i < bucket_ranges()->bucket_count(); ++i) {
     if (!pickle->WriteInt(bucket_ranges()->range(i)))
       return false;
   }
@@ skipping 42 matching lines @@
   for (size_t i = 0; i < custom_ranges.size(); i++) {
     Sample sample = custom_ranges[i];
     if (sample < 0 || sample > HistogramBase::kSampleType_MAX - 1)
       return false;
     if (sample != 0)
       has_valid_range = true;
   }
   return has_valid_range;
 }
 
-// static
-BucketRanges* CustomHistogram::CreateBucketRangesFromCustomRanges(
-      const std::vector<Sample>& custom_ranges) {
-  // Remove the duplicates in the custom ranges array.
-  std::vector<int> ranges = custom_ranges;
-  ranges.push_back(0);  // Ensure we have a zero value.
-  ranges.push_back(HistogramBase::kSampleType_MAX);
-  std::sort(ranges.begin(), ranges.end());
-  ranges.erase(std::unique(ranges.begin(), ranges.end()), ranges.end());
-
-  BucketRanges* bucket_ranges = new BucketRanges(ranges.size());
-  for (size_t i = 0; i < ranges.size(); i++) {
-    bucket_ranges->set_range(i, ranges[i]);
-  }
-  bucket_ranges->ResetChecksum();
-  return bucket_ranges;
-}
-
 }  // namespace base