Support using UMA_HISTOGRAM_CUSTOM_ENUMERATION from the renderer.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index 7077b090715d6bab39ab489435cbb97f3af133db..a44a2eb8888a517eef35f134737def5d9f46d760 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -239,13 +239,16 @@ std::string Histogram::SerializeHistogramInfo(const Histogram& histogram,
   pickle.WriteInt(histogram.flags());
 
   snapshot.Serialize(&pickle);
+
+  histogram.SerializeRanges(&pickle);
+
   return std::string(static_cast<const char*>(pickle.data()), pickle.size());
 }
 
 // static
 bool Histogram::DeserializeHistogramInfo(const std::string& histogram_info) {
   if (histogram_info.empty()) {
-      return false;
+    return false;
   }
 
   Pickle pickle(histogram_info.data(),
@@ -271,6 +274,7 @@ bool Histogram::DeserializeHistogramInfo(const std::string& histogram_info) {
     DLOG(ERROR) << "Pickle error decoding Histogram: " << histogram_name;
     return false;
   }
+
   DCHECK(pickle_flags & kIPCSerializationSourceFlag);
   // Since these fields may have come from an untrusted renderer, do additional
   // checks above and beyond those in Histogram::Initialize()
@@ -294,6 +298,14 @@ bool Histogram::DeserializeHistogramInfo(const std::string& histogram_info) {
         histogram_name, declared_min, declared_max, bucket_count, flags);
   } else if (histogram_type == BOOLEAN_HISTOGRAM) {
     render_histogram = BooleanHistogram::FactoryGet(histogram_name, flags);
+  } else if (histogram_type == CUSTOM_HISTOGRAM) {
+    std::vector<Histogram::Sample> sample_ranges(bucket_count);
+    if (!CustomHistogram::DeserializeRanges(&iter, pickle, &sample_ranges)) {
+      DLOG(ERROR) << "Pickle error decoding ranges: " << histogram_name;
+      return false;
+    }
+    render_histogram =
+        CustomHistogram::FactoryGet(histogram_name, sample_ranges, flags);
   } else {
     DLOG(ERROR) << "Error Deserializing Histogram Unknown histogram_type: "
                 << histogram_type;
@@ -440,6 +452,10 @@ Histogram::~Histogram() {
   DCHECK(ValidateBucketRanges());
 }
 
+bool Histogram::SerializeRanges(Pickle* pickle) const {
+  return true;
+}
+
 // 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
@@ -981,6 +997,24 @@ CustomHistogram::CustomHistogram(const std::string& name,
   DCHECK_EQ(custom_ranges[0], 0);
 }
 
+bool CustomHistogram::SerializeRanges(Pickle* pickle) const {
+  for (size_t i = 0; i < cached_ranges()->size(); ++i) {
+    if (!pickle->WriteInt(cached_ranges()->ranges(i)))
+      return false;
+  }
+  return true;
+}
+
+// static
+bool CustomHistogram::DeserializeRanges(
+    void** iter, const Pickle& pickle, std::vector<Histogram::Sample>* ranges) {
+  for (size_t i = 0; i < ranges->size(); ++i) {
+    if (!pickle.ReadInt(iter, &(*ranges)[i]))
+      return false;
+  }
+  return true;
+}
+
 void CustomHistogram::InitializedCustomBucketRange(
     const std::vector<Sample>& custom_ranges) {
   DCHECK_GT(custom_ranges.size(), 1u);