Avoid using ToInternalValue in computing timings, so that the timings are consistent accross platfo…

components/startup_metric_utils/startup_metric_utils.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 "components/startup_metric_utils/startup_metric_utils.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/environment.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 29 matching lines @@
   return slow_startup_time_hash_lock;
 }
 
 // Record time of main entry so it can be read from Telemetry performance
 // tests.
 // TODO(jeremy): Remove once crbug.com/317481 is fixed.
 void RecordMainEntryTimeHistogram() {
   const int kLowWordMask = 0xFFFFFFFF;
   const int kLower31BitsMask = 0x7FFFFFFF;
   base::TimeDelta browser_main_entry_time_absolute =
-      base::TimeDelta::FromMilliseconds(
-          MainEntryPointTimeInternal()->ToInternalValue() / 1000.0);
+      *MainEntryPointTimeInternal() - base::Time::UnixEpoch();
 
   uint64 browser_main_entry_time_raw_ms =
       browser_main_entry_time_absolute.InMilliseconds();
 
   base::TimeDelta browser_main_entry_time_raw_ms_high_word =
       base::TimeDelta::FromMilliseconds(
           (browser_main_entry_time_raw_ms >> 32) & kLowWordMask);
   // Shift by one because histograms only support non-negative values.
   base::TimeDelta browser_main_entry_time_raw_ms_low_word =
       base::TimeDelta::FromMilliseconds(
@@ skipping 181 matching lines @@
   SubsystemStartupTimeHash* hash = GetSubsystemStartupTimeHash();
   // Only record the initial sample for a given histogram.
   if (hash->find(histogram_name_) !=  hash->end())
     return;
 
   (*hash)[histogram_name_] =
       base::TimeTicks::Now() - start_time_;
 }
 
 }  // namespace startup_metric_utils