Collect information about failing histogram factory calls.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index ea4f8167fa28cc7098ce233cddbd7ed77fd23a77..09d134965c80a8a605cb313dcc969e52a5de9d41 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -154,10 +154,18 @@ HistogramBase* Histogram::Factory::Build() {
   ImportPersistentHistograms();
 
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name_);
+
+  // crbug.com/588946 debugging. See comment at end of function.
+  const BucketRanges* created_ranges;

[Alexei Svitkine (slow), 2016/02/26 19:12:50]

Please initialize these to nullptr or something, else these will have garbage
values if the if below doesn't run.

[bcwhite, 2016/02/26 20:31:18]

Done.

+  const BucketRanges* registered_ranges;
+  PersistentMemoryAllocator::Reference histogram_ref;
+  HistogramBase* tentative_histogram;
+  PersistentMemoryAllocator* allocator;
+
   if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
-    const BucketRanges* created_ranges = CreateRanges();
-    const BucketRanges* registered_ranges =
+    created_ranges = CreateRanges();
+    registered_ranges =
         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(created_ranges);
 
     // In most cases, the bucket-count, minimum, and maximum values are known
@@ -176,9 +184,9 @@ HistogramBase* Histogram::Factory::Build() {
     // that is off by default. If the allocator doesn't exist or if
     // allocating from it fails, code below will allocate the histogram from
     // the process heap.
-    PersistentMemoryAllocator::Reference histogram_ref = 0;
-    HistogramBase* tentative_histogram = nullptr;
-    PersistentMemoryAllocator* allocator =
+    histogram_ref = 0;
+    tentative_histogram = nullptr;
+    allocator =
         GetPersistentHistogramMemoryAllocator();
     if (allocator) {
       flags_ |= HistogramBase::kIsPersistent;
@@ -223,8 +231,36 @@ HistogramBase* Histogram::Factory::Build() {
     // on dereference, but extension/Pepper APIs will guard against NULL and not
     // crash.
     DLOG(ERROR) << "Histogram " << name_ << " has bad construction arguments";
-    return nullptr;
+    histogram = nullptr;
+  }
+
+#if !DCHECK_IS_ON()  // Don't affect tests, only release builds.
+  // For the moment, crash here so that collected crash reports have access
+  // to the construction values in order to figure out why this is failing.
+  // TODO(bcwhite): Remove this once crbug.com/588946 is resolved. Also remove
+  // from beta-branch because we don't want crashes due to misbehaving
+  // extensions (see comment above).
+  if (!histogram) {
+    HistogramType histogram_type = histogram_type_;
+    HistogramBase::Sample minimum = minimum_;
+    HistogramBase::Sample maximum = maximum_;
+    uint32_t bucket_count = bucket_count_;
+    int32_t flags = flags_;
+    CHECK(histogram);
+    base::debug::Alias(&histogram_type);
+    base::debug::Alias(&minimum);
+    base::debug::Alias(&maximum);
+    base::debug::Alias(&bucket_count);
+    base::debug::Alias(&flags);
+    base::debug::Alias(&created_ranges);
+    base::debug::Alias(&registered_ranges);
+    base::debug::Alias(&histogram_ref);
+    base::debug::Alias(&tentative_histogram);
+    base::debug::Alias(&allocator);
+    base::debug::Alias(&tentative_histogram);
   }
+#endif
+
   return histogram;
 }