Field-check ranges creation.

Check if the original ranges creation is causing the bad bucket
values or if its some kind of corruption since the last time.

Bug: 836238
Change-Id: I5b2b72504b6ac6437a9cec3ee42ae7e688be451b
Reviewed-on: https://chromium-review.googlesource.com/1234215Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592484}

base/metrics/histogram.cc

@@ -168,9 +168,56 @@ HistogramBase* Histogram::Factory::Build() {
       return DummyHistogram::GetInstance();
     // To avoid racy destruction at shutdown, the following will be leaked.
     const BucketRanges* created_ranges = CreateRanges();
+
+// Temporary check for https://crbug.com/836238
+#if defined(OS_WIN)  // Only Windows has a debugger that makes this useful.
+    if (bucket_count_ > 0 &&
+        maximum_ != created_ranges->range(bucket_count_ - 1)) {
+      // Create local copies of the parameters to be sure they'll be available
+      // in the crash dump for the debugger to see.
+      DEBUG_ALIAS_FOR_CSTR(h_name, name_.c_str(), 100);
+      HistogramType h_type = histogram_type_;
+      Sample h_min = minimum_;
+      Sample h_max = maximum_;
+      uint32_t h_count = bucket_count_;
+      debug::Alias(&h_type);
+      debug::Alias(&h_min);
+      debug::Alias(&h_max);
+      debug::Alias(&h_count);
+      uint32_t ranges_min = created_ranges->range(1);
+      uint32_t ranges_max = created_ranges->range(bucket_count_ - 1);
+      debug::Alias(&ranges_min);
+      debug::Alias(&ranges_max);
+      CHECK(false) << name_;
+    }
+#endif
+
     const BucketRanges* registered_ranges =
         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(created_ranges);
 
+// Temporary check for https://crbug.com/836238
+#if defined(OS_WIN)  // Only Windows has a debugger that makes this useful.
+    std::unique_ptr<const BucketRanges> recreated_ranges(CreateRanges());
+    for (uint32_t i = 0; i < bucket_count_; ++i) {
+      uint32_t created_range = recreated_ranges->range(i);
+      uint32_t registered_range = registered_ranges->range(i);
+      if (created_range != registered_range) {
+        // Create local copies of the parameters to be sure they'll be available
+        // in the crash dump for the debugger to see.
+        DEBUG_ALIAS_FOR_CSTR(h_name, name_.c_str(), 100);
+        HistogramType h_type = histogram_type_;
+        uint32_t b_count = bucket_count_;
+        size_t c_count = recreated_ranges->size();
+        size_t r_count = registered_ranges->size();
+        debug::Alias(&h_type);
+        debug::Alias(&b_count);
+        debug::Alias(&c_count);
+        debug::Alias(&r_count);
+        CHECK(false) << name_;
+      }
+    }
+#endif
+
     // In most cases, the bucket-count, minimum, and maximum values are known
     // when the code is written and so are passed in explicitly. In other
     // cases (such as with a CustomHistogram), they are calculated dynamically