Add debug info for field trial allocation crash

base/metrics/field_trial.h

Index: base/metrics/field_trial.h
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index 306f0075c6657d04c6e23f95a41e8dce455e37a3..98361732994ddb8bc35368d420c5edc7d11acb7a 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -84,6 +84,9 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
  public:
   typedef int Probability;  // Probability type for being selected in a trial.
 
+  // TODO(665129): Make private again after crash has been resolved.
+  typedef SharedPersistentMemoryAllocator::Reference FieldTrialRef;
+
   // Specifies the persistence of the field trial group choice.
   enum RandomizationType {
     // One time randomized trials will persist the group choice between
@@ -219,8 +222,6 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, FloatBoundariesGiveEqualGroupSizes);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, DoesNotSurpassTotalProbability);
 
-  typedef SharedPersistentMemoryAllocator::Reference FieldTrialRef;
-
   friend class base::FieldTrialList;
 
   friend class RefCounted<FieldTrial>;