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

chrome/chrome_features.gypi

Index: chrome/chrome_features.gypi
diff --git a/chrome/chrome_features.gypi b/chrome/chrome_features.gypi
index 3c80aa0af27fccc438fb5c02c339f33fe6a8de47..e3f0c001055cc38b88b4b71e9889dc4e9ae08fab 100644
--- a/chrome/chrome_features.gypi
+++ b/chrome/chrome_features.gypi
@@ -21,6 +21,11 @@
         }, {
           'enable_background%': 1,
           'enable_google_now%': 1,
+        }],
+        ['chrome_pgo_phase!=0', {
+          'pgo_build%': 1,
+        }, {
+          'pgo_build%': 0,
         }]
       ],
 
@@ -35,6 +40,7 @@
     '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,