Collect information about failing histogram factory calls.

base/metrics/metrics_hashes.cc

 // Copyright 2014 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.
 
 #include "base/metrics/metrics_hashes.h"
 
+#include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/md5.h"
 #include "base/sys_byteorder.h"
 
 namespace base {
 
 namespace {
 
 // Converts the 8-byte prefix of an MD5 hash into a uint64_t value.
 inline uint64_t DigestToUInt64(const base::MD5Digest& digest) {
   uint64_t value;
-  DCHECK_GE(sizeof(digest.a), sizeof(value));
+  CHECK_GE(sizeof(digest.a), sizeof(value));
   memcpy(&value, digest.a, sizeof(value));
-  return base::NetToHost64(value);
+  uint64_t hash = base::NetToHost64(value);
+  CHECK_NE(0U, hash);
+  base::debug::Alias(&hash);
+  base::debug::Alias(&value);
+  base::debug::Alias(&digest);
+  return hash;
 }
 
 }  // namespace
 
 uint64_t HashMetricName(base::StringPiece name) {
-  base::MD5Digest digest;
+  base::MD5Digest digest = {{
+    0x0F, 0x0E, 0x0D, 0x0C, 0x00, 0x0D, 0x0E, 0x02,
+    0x0D, 0x0E, 0x0A, 0x0D, 0x0B, 0x0E, 0x0E, 0x0F
+  }};
   base::MD5Sum(name.data(), name.size(), &digest);
+  CHECK(
+      digest.a[0] != 0x0F ||
+      digest.a[1] != 0x0E ||
+      digest.a[2] != 0x0D ||
+      digest.a[3] != 0x0C ||
+      digest.a[4] != 0x00 ||
+      digest.a[5] != 0x0D ||
+      digest.a[6] != 0x0E ||
+      digest.a[7] != 0x02 ||
+      digest.a[8] != 0x0D ||
+      digest.a[9] != 0x0E ||
+      digest.a[10] != 0x0A ||
+      digest.a[11] != 0x0D ||
+      digest.a[12] != 0x0B ||
+      digest.a[13] != 0x0E ||
+      digest.a[14] != 0x0E ||
+      digest.a[15] != 0x0F);
+  base::debug::Alias(&name);
   return DigestToUInt64(digest);
 }
 
 }  // namespace metrics