Try to detect internal corruption of histogram instances....

chrome/renderer/renderer_histogram_snapshots.cc

Index: chrome/renderer/renderer_histogram_snapshots.cc
===================================================================
--- chrome/renderer/renderer_histogram_snapshots.cc	(revision 64486)
+++ chrome/renderer/renderer_histogram_snapshots.cc	(working copy)
@@ -52,17 +52,33 @@
           sequence_number, pickled_histograms));
 }
 
-// Extract snapshot data and then send it off the the Browser process
-// to save it.
+// Extract snapshot data, remember what we've seen so far, and then send off the
+// delta to the browser.
 void RendererHistogramSnapshots::UploadHistrogram(
     const Histogram& histogram,
     HistogramPickledList* pickled_histograms) {
-
   // 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 the browser.
+    UMA_HISTOGRAM_ENUMERATION("Histogram.InconsistenciesRenderer",
+                              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.InconsistenciesRendererUnique",
+                              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;
@@ -89,7 +105,6 @@
     const Histogram& histogram,
     const Histogram::SampleSet& snapshot,
     HistogramPickledList* pickled_histograms) {
-
   DCHECK(0 != snapshot.TotalCount());
   snapshot.CheckSize(histogram);