Allow histograms in cache stats.cc to bypass corruption checks

This is a relanding of http://codereview.chromium.org/4174002

The change in this CL is that I've made the function
to look for errors virtual, and over-rode it in StatsHistograms.
The current override doesn't actually check for inconsistencies,
so that the UMA checks (and renderer-to-histogram checks) won't
complain and refuse to transport the histograms.

BUG=61281
r=rvargas
Review URL: http://codereview.chromium.org/4364001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64990 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 19 insertions, 4 deletions

diff --git a/chrome/renderer/renderer_histogram_snapshots.cc b/chrome/renderer/renderer_histogram_snapshots.cc
index ae9ee1d..6124e04 100644
--- a/chrome/renderer/renderer_histogram_snapshots.cc
+++ b/chrome/renderer/renderer_histogram_snapshots.cc
@@ -52,17 +52,33 @@ void RendererHistogramSnapshots::UploadAllHistrograms(int sequence_number) {
           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 @@ void RendererHistogramSnapshots::UploadHistogramDelta(
     const Histogram& histogram,
     const Histogram::SampleSet& snapshot,
     HistogramPickledList* pickled_histograms) {
-
   DCHECK(0 != snapshot.TotalCount());
   snapshot.CheckSize(histogram);