Add a PGO tag for the PGO builds in chrome://version

chrome/chrome_features.gypi

 # Copyright 2015 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.
 
 # This is the GYP equivalent of //chrome/common/features.gni.
 # Please keep in sync!
 
 {
   'variables': {
     'variables': {
       # Conditional variables.
       'conditions': [
         ['OS=="android"', {
           'android_java_ui%': 1,
         }, {
           'android_java_ui': 0,
         }],
         ['OS=="android" or OS=="ios"', {
           'enable_background%': 0,
           'enable_google_now%': 0,
         }, {
           'enable_background%': 1,
           'enable_google_now%': 1,
+        }],
+        ['chrome_pgo_phase!=0', {
+          'pgo_build%': 1,
+        }, {
+          'pgo_build%': 0,
         }]
       ],
 
       # Use vulcanized HTML/CSS/JS resources to speed up WebUI (chrome://)
       # pages. https://github.com/polymer/vulcanize
       'use_vulcanize%': 1,
     },
 
     # Anything in the conditions needs to be copied to the outer scope to be
     # accessible.
     'enable_background%': '<(enable_background)',
     'enable_google_now%': '<(enable_google_now)',
     'android_java_ui%': '<(android_java_ui)',
     'use_vulcanize%': '<(use_vulcanize)',
+    'pgo_build%': '<(pgo_build)',
 
     # GN only, but defined here so BUILDFLAG works without ifdef.
     'enable_package_mash_services%': 0,
 
     # Grit defines based on the feature flags. These must be manually added to
     # grit targets.
     'chrome_grit_defines': [
       '-D', 'enable_background=<(enable_background)',
       '-D', 'enable_google_now=<(enable_google_now)',
       '-D', 'use_vulcanize=<(use_vulcanize)',
     ],
   },
 }