Revert 64687 - Try to detect internal corruption of histogram instances....

base/metrics/histogram.h

Index: base/metrics/histogram.h
===================================================================
--- base/metrics/histogram.h	(revision 64845)
+++ base/metrics/histogram.h	(working copy)
@@ -36,7 +36,6 @@
 #include <string>
 #include <vector>
 
-#include "base/gtest_prod_util.h"
 #include "base/ref_counted.h"
 #include "base/logging.h"
 #include "base/time.h"
@@ -244,8 +243,8 @@
   typedef std::vector<Count> Counts;
   typedef std::vector<Sample> Ranges;
 
-  // These enums are used to facilitate deserialization of renderer histograms
-  // into the browser.
+  /* These enums are meant to facilitate deserialization of renderer histograms
+     into the browser. */
   enum ClassType {
     HISTOGRAM,
     LINEAR_HISTOGRAM,
@@ -274,16 +273,6 @@
     kHexRangePrintingFlag = 0x8000,  // Fancy bucket-naming supported.
   };
 
-  enum Inconsistencies {
-    NO_INCONSISTENCIES = 0x0,
-    RANGE_CHECKSUM_ERROR = 0x1,
-    BUCKET_ORDER_ERROR = 0x2,
-    COUNT_HIGH_ERROR = 0x4,
-    COUNT_LOW_ERROR = 0x8,
-
-    NEVER_EXCEEDED_VALUE = 0x10
-  };
-
   struct DescriptionPair {
     Sample sample;
     const char* description;  // Null means end of a list of pairs.
@@ -309,7 +298,6 @@
     Count TotalCount() const;
     int64 sum() const { return sum_; }
     int64 square_sum() const { return square_sum_; }
-    int64 redundant_count() const { return redundant_count_; }
 
     // Arithmetic manipulation of corresponding elements of the set.
     void Add(const SampleSet& other);
@@ -327,21 +315,7 @@
     // without shared memory at some point.
     int64 sum_;         // sum of samples.
     int64 square_sum_;  // sum of squares of samples.
-
-   private:
-    // Allow tests to corrupt our innards for testing purposes.
-    FRIEND_TEST(HistogramTest, CorruptSampleCounts);
-
-    // To help identify memory corruption, we reduntantly save the number of
-    // samples we've accumulated into all of our buckets.  We can compare this
-    // count to the sum of the counts in all buckets, and detect problems.  Note
-    // that due to races in histogram accumulation (if a histogram is indeed
-    // updated on several threads simultaneously), the tallies might mismatch,
-    // and also the snapshotting code may asynchronously get a mismatch (though
-    // generally either race based mismatch cause is VERY rare).
-    int64 redundant_count_;
   };
-
   //----------------------------------------------------------------------------
   // minimum should start from 1. 0 is invalid as a minimum. 0 is an implicit
   // default underflow bucket.
@@ -393,13 +367,6 @@
   // browser process.
   static bool DeserializeHistogramInfo(const std::string& histogram_info);
 
-  // Check to see if bucket ranges, counts and tallies in the snapshot are
-  // consistent with the bucket ranges and checksums in our histogram.  This can
-  // produce a false-alarm if a race occurred in the reading of the data during
-  // a SnapShot process, but should otherwise be false at all times (unless we
-  // have memory over-writes, or DRAM failures).
-  Inconsistencies FindCorruption(const SampleSet& snapshot) const;
-
   //----------------------------------------------------------------------------
   // Accessors for factory constuction, serialization and testing.
   //----------------------------------------------------------------------------
@@ -408,7 +375,6 @@
   Sample declared_min() const { return declared_min_; }
   Sample declared_max() const { return declared_max_; }
   virtual Sample ranges(size_t i) const { return ranges_[i];}
-  Sample range_checksum() const { return range_checksum_; }
   virtual size_t bucket_count() const { return bucket_count_; }
   // Snapshot the current complete set of sample data.
   // Override with atomic/locked snapshot if needed.
@@ -443,9 +409,6 @@
   // Get normalized size, relative to the ranges_[i].
   virtual double GetBucketSize(Count current, size_t i) const;
 
-  // Recalculate range_checksum_.
-  void ResetRangeChecksum();
-
   // Return a string description of what goes in a given bucket.
   // Most commonly this is the numeric value, but in derived classes it may
   // be a name (or string description) given to the bucket.
@@ -467,18 +430,9 @@
   bool ValidateBucketRanges() const;
 
  private:
-  // Allow tests to corrupt our innards for testing purposes.
-  FRIEND_TEST(HistogramTest, CorruptBucketBounds);
-  FRIEND_TEST(HistogramTest, CorruptSampleCounts);
-
   // Post constructor initialization.
   void Initialize();
 
-  // Return true iff the range_checksum_ matches current ranges_ vector.
-  bool HasValidRangeChecksum() const;
-
-  Sample CalculateRangeChecksum() const;
-
   //----------------------------------------------------------------------------
   // Helpers for emitting Ascii graphic.  Each method appends data to output.
 
@@ -523,11 +477,6 @@
   // The dimension of ranges_ is bucket_count + 1.
   Ranges ranges_;
 
-  // For redundancy, we store the sum of all the sample ranges when ranges are
-  // generated.  If ever there is ever a difference, then the histogram must
-  // have been corrupted.
-  Sample range_checksum_;
-
   // Finally, provide the state that changes with the addition of each new
   // sample.
   SampleSet sample_;
@@ -612,11 +561,11 @@
   virtual ClassType histogram_type() const;
 
   static scoped_refptr<Histogram> FactoryGet(const std::string& name,
-      const std::vector<Sample>& custom_ranges, Flags flags);
+      const std::vector<int>& custom_ranges, Flags flags);
 
  protected:
   CustomHistogram(const std::string& name,
-                  const std::vector<Sample>& custom_ranges);
+                  const std::vector<int>& custom_ranges);
 
   // Initialize ranges_ mapping.
   virtual void InitializeBucketRange();
@@ -624,7 +573,7 @@
 
  private:
   // Temporary pointer used during construction/initialization, and then NULLed.
-  const std::vector<Sample>* ranges_vector_;
+  const std::vector<int>* ranges_vector_;
 
   DISALLOW_COPY_AND_ASSIGN(CustomHistogram);
 };