Try to detect internal corruption of histogram instances.

Corruptions can include changes in bucket boundaries,
large changes in sample counts (in a bucket), etc.

We now detect problems, and don't forward the corrupt
data any further. This means it won't exit the renderer
and go to the browser if corrupt, and it won't exit
the browser and be sent up via UMA if corrupt.

IF the would-be corruption is caused by a race to
snapshot the data, then a later snapshot should get
the clean copy, and all data (across the precluded
period) will be sent onward.

BUG=61281
r=mbelshe
Review URL: http://codereview.chromium.org/4174002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64687 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 17 insertions, 1 deletions

diff --git a/chrome/common/metrics_helpers.cc b/chrome/common/metrics_helpers.cc
index 6dd0a42..e25355c 100644
--- a/chrome/common/metrics_helpers.cc
+++ b/chrome/common/metrics_helpers.cc
@@ -484,9 +484,25 @@ void MetricsServiceBase::RecordHistogram(const Histogram& histogram) {
   // Get up-to-date snapshot of sample stats.
   Histogram::SampleSet snapshot;
   histogram.SnapshotSample(&snapshot);
-
   const std::string& histogram_name = histogram.histogram_name();
 
+  int corruption = histogram.FindCorruption(snapshot);
+  if (corruption) {
+    NOTREACHED();
+    // Don't send corrupt data to metrics survices.
+    UMA_HISTOGRAM_ENUMERATION("Histogram.InconsistenciesBrowser",
+                              corruption, Histogram::NEVER_EXCEEDED_VALUE);
+    typedef std::map<std::string, int> ProblemMap;
+    static ProblemMap* inconsistencies = new ProblemMap;
+    int old_corruption = (*inconsistencies)[histogram_name];
+    if (old_corruption == (corruption | old_corruption))
+      return;  // We've already seen this corruption for this histogram.
+    (*inconsistencies)[histogram_name] |= corruption;
+    UMA_HISTOGRAM_ENUMERATION("Histogram.InconsistenciesBrowserUnique",
+                              corruption, Histogram::NEVER_EXCEEDED_VALUE);
+    return;
+  }
+
   // Find the already sent stats, or create an empty set.
   LoggedSampleMap::iterator it = logged_samples_.find(histogram_name);
   Histogram::SampleSet* already_logged;