Use ElapsedTimer to measure VS files generation time in GN

tools/gn/command_gen.cc

 // Copyright (c) 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 "base/atomicops.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/timer/elapsed_timer.h"
@@ skipping 134 matching lines @@
                                     errors_found), DECORATION_YELLOW);
   }
   return false;
 }
 
 bool RunIdeWriter(const std::string& ide,
                   const BuildSettings* build_settings,
                   Builder* builder,
                   Err* err) {
   if (ide == kSwitchIdeValueVs) {
-    base::TimeTicks begin_vs_gen = base::TimeTicks::Now();
+    base::ElapsedTimer timer;
     bool res =
         VisualStudioWriter::RunAndWriteFiles(build_settings, builder, err);
     if (res &&
         !base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kQuiet)) {
-      OutputString(
-          "Generating Visual Studio projects took " +
-          base::Int64ToString(
-              (base::TimeTicks::Now() - begin_vs_gen).InMilliseconds()) +
-          "ms\n");
+      OutputString("Generating Visual Studio projects took " +
+                   base::Int64ToString(timer.Elapsed().InMilliseconds()) +
+                   "ms\n");
     }
     return res;
   }
 
   *err = Err(Location(), "Unknown IDE: " + ide);
   return false;
 }
 
 }  // namespace
 
@@ skipping 86 matching lines @@
             setup->scheduler().input_file_manager()->GetInputFileCount()) +
         " files in " +
         base::Int64ToString(elapsed_time.InMilliseconds()) + "ms\n";
     OutputString(stats);
   }
 
   return 0;
 }
 
 }  // namespace commands