Add WARN_UNUSED_RESULT to base::Time methods that return bool.

components/metrics/data_use_tracker.cc

 // Copyright 2016 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 "components/metrics/data_use_tracker.h"
 
 #include <string>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
@@ skipping 100 matching lines @@
 
   const base::DictionaryValue* user_pref_dict =
       local_state_->GetDictionary(pref_name);
   const base::Time current_date = GetCurrentMeasurementDate();
   const base::Time week_ago = current_date - base::TimeDelta::FromDays(7);
 
   base::DictionaryValue user_pref_new_dict;
   for (base::DictionaryValue::Iterator it(*user_pref_dict); !it.IsAtEnd();
        it.Advance()) {
     base::Time key_date;
-    base::Time::FromUTCString(it.key().c_str(), &key_date);
-    if (key_date > week_ago)
+    if (base::Time::FromUTCString(it.key().c_str(), &key_date) &&
+        key_date > week_ago)
       user_pref_new_dict.Set(it.key(), it.value().CreateDeepCopy());
   }
   local_state_->Set(pref_name, user_pref_new_dict);
 }
 
 // Note: We compute total data use regardless of what is the current date. In
 // scenario when user travels back in time zone and current date becomes earlier
 // than latest registered date in perf, we still count that in total use as user
 // actually used that data.
 int DataUseTracker::ComputeTotalDataUse(const std::string& pref_name) {
@@ skipping 42 matching lines @@
 std::string DataUseTracker::GetCurrentMeasurementDateAsString() const {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   base::Time::Exploded today_exploded;
   GetCurrentMeasurementDate().LocalExplode(&today_exploded);
   return base::StringPrintf("%04d-%02d-%02d", today_exploded.year,
                             today_exploded.month, today_exploded.day_of_month);
 }
 
 }  // namespace metrics