Crash when we notice a corruption of the histogram range-vector...

chrome/common/metrics_helpers.cc

 // Copyright (c) 2010 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 "chrome/common/metrics_helpers.h"
 
 #if defined(USE_SYSTEM_LIBBZ2)
 #include <bzlib.h>
 #else
 #include "third_party/bzip2/bzlib.h"
@@ skipping 513 matching lines @@
   }
 }
 
 void HistogramSender::TransmitHistogram(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);
+
+  // Crash if we detect that our histograms have been overwritten.  This may be
+  // a fair distance from the memory smasher, but we hope to correlate these
+  // crashes with other events, such as plugins, or usage patterns, etc.
+  if (Histogram::BUCKET_ORDER_ERROR & corruption) {
+    // The checksum should have caught this, so crash separately if it didn't.
+    CHECK_NE(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+    CHECK(false);  // Crash for the bucket order corruption.
+  }
+  // Checksum corruption might not have caused order corruption.
+  CHECK_EQ(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+
   if (corruption) {
     NOTREACHED();
     InconsistencyDetected(corruption);
     // Don't send corrupt data to metrics survices.
     if (NULL == inconsistencies_.get())
       inconsistencies_.reset(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;
@@ skipping 28 matching lines @@
     snapshot.Subtract(*already_logged);
   }
 
   // Snapshot now contains only a delta to what we've already_logged.
   if (snapshot.redundant_count() > 0) {
     TransmitHistogramDelta(histogram, snapshot);
     // Add new data into our running total.
     already_logged->Add(snapshot);
   }
 }