Add back in log info about histogram hashes

This was seemingly inadvertently deleted in a CL

http://src.chromium.org/viewvc/chrome?view=rev&revision=16023

The change should have no semantic impact on the running of the program
(unless the user enables logging), and it helps me isolate actual names
of histograms for unknown hashes that appear on the histogram dashboard.

r=evanm,dpranke
Review URL: http://codereview.chromium.org/125011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18280 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 8 insertions, 0 deletions

diff --git a/chrome/browser/metrics/metrics_log.cc b/chrome/browser/metrics/metrics_log.cc
index 7d81bce..2d00123 100644
--- a/chrome/browser/metrics/metrics_log.cc
+++ b/chrome/browser/metrics/metrics_log.cc
@@ -112,6 +112,14 @@ std::string MetricsLog::CreateHash(const std::string& value) {
   DCHECK(arraysize(digest.a) >= arraysize(reverse));
   for (size_t i = 0; i < arraysize(reverse); ++i)
     reverse[i] = digest.a[arraysize(reverse) - i - 1];
+  // The following log is VERY helpful when folks add some named histogram into
+  // the code, but forgot to update the descriptive list of histograms.  When
+  // that happens, all we get to see (server side) is a hash of the histogram
+  // name.  We can then use this logging to find out what histogram name was
+  // being hashed to a given MD5 value by just running the version of Chromium
+  // in question with --enable-logging.
+  LOG(INFO) << "Metrics: Hash numeric [" << value << "]=["
+      << *reinterpret_cast<const uint64*>(&reverse[0]) << "]";
   return std::string(reinterpret_cast<char*>(digest.a), arraysize(digest.a));
 }