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..a6f2b27b9005eb560cfd5c419acd2692f7d54931 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -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 =