GCAPI should append to the existing experiment_labels instead of clobbering them.

chrome/installer/util/google_update_experiment_util.cc

 // Copyright 2013 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 "chrome/installer/util/google_update_experiment_util.h"
 
 #include <vector>
 
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 
 namespace installer {
 
 namespace {
 
 const char* const kDays[] =
     { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
 
 const char* const kMonths[] =
     { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
       "Oct", "Nov", "Dec"};
 
 }
 
-string16 BuildExperimentDateString() {
+string16 BuildExperimentDateString(const base::Time& current_time) {
   // The Google Update experiment_labels timestamp format is:
   // "DAY, DD0 MON YYYY HH0:MI0:SE0 TZ"
   //  DAY = 3 character day of week,
   //  DD0 = 2 digit day of month,
   //  MON = 3 character month of year,
   //  YYYY = 4 digit year,
   //  HH0 = 2 digit hour,
   //  MI0 = 2 digit minute,
   //  SE0 = 2 digit second,
   //  TZ = 3 character timezone
   base::Time::Exploded then = {};
-  base::Time::Now().UTCExplode(&then);
+  current_time.UTCExplode(&then);
   then.year += 1;
   DCHECK(then.HasValidValues());
 
   return UTF8ToUTF16(base::StringPrintf("%s, %02d %s %d %02d:%02d:%02d GMT",
                                         kDays[then.day_of_week],
                                         then.day_of_month,
                                         kMonths[then.month - 1],
                                         then.year,
                                         then.hour,
                                         then.minute,
                                         then.second));
 }
 
 }  // namespace installer