Minor fixes in FieldTrial.

base/metrics/field_trial.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/field_trial.h"
 
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
@@ skipping 23 matching lines @@
                        const int year,
                        const int month,
                        const int day_of_month)
   : name_(name),
     divisor_(total_probability),
     default_group_name_(default_group_name),
     random_(static_cast<Probability>(divisor_ * base::RandDouble())),
     accumulated_group_probability_(0),
     next_group_number_(kDefaultGroupNumber+1),
     group_(kNotFinalized) {
+  DCHECK_GT(total_probability, 0);
   DCHECK(!default_group_name_.empty());
   FieldTrialList::Register(this);
 
   DCHECK_GT(year, 1970);
   DCHECK_GT(month, 0);
   DCHECK_LT(month, 13);
   DCHECK_GT(day_of_month, 0);
   DCHECK_LT(day_of_month, 32);
 
   base::Time::Exploded exploded;
   exploded.year = year;
   exploded.month = month;
-  exploded.day_of_week = 0;  // Should be unusued.
+  exploded.day_of_week = 0;  // Should be unused.
   exploded.day_of_month = day_of_month;
   exploded.hour = 0;
   exploded.minute = 0;
   exploded.second = 0;
   exploded.millisecond = 0;
 
   base::Time expiration_time = Time::FromLocalExploded(exploded);
   disable_field_trial_ = (GetBuildTime() > expiration_time) ? true : false;
 }
 
@@ skipping 196 matching lines @@
 }
 
 FieldTrial* FieldTrialList::PreLockedFind(const std::string& name) {
   RegistrationList::iterator it = registered_.find(name);
   if (registered_.end() == it)
     return NULL;
   return it->second;
 }
 
 }  // namespace base