Prevent calling internal metrics code with invalid values.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index a44a2eb8888a517eef35f134737def5d9f46d760..180c36a157a52c35871a5702ce68b65e58df6376 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -94,6 +94,10 @@ Histogram* Histogram::FactoryGet(const std::string& name,
   if (maximum > kSampleType_MAX - 1)
     maximum = kSampleType_MAX - 1;
 
+  DCHECK_GT(maximum, minimum);
+  DCHECK_GT((Sample) bucket_count, 2);
+  DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
+
   if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
     // Extra variable is not needed... but this keeps this section basically
     // identical to other derived classes in this file (and compiler will
@@ -816,6 +820,10 @@ Histogram* LinearHistogram::FactoryGet(const std::string& name,
   if (maximum > kSampleType_MAX - 1)
     maximum = kSampleType_MAX - 1;
 
+  DCHECK_GT(maximum, minimum);
+  DCHECK_GT((Sample) bucket_count, 2);
+  DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
+
   if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     LinearHistogram* tentative_histogram =