Enable WPO for the x64 Official builds.

build/config/compiler/compiler.gni

 # 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 12 matching lines @@
 
   # Specify the current PGO phase, only used for the Windows MSVS build. Here's
   # the different values that can be used:
   #     0 : Means that PGO is turned off.
   #     1 : Used during the PGI (instrumentation) phase.
   #     2 : Used during the PGO (optimization) phase.
   #
   # TODO(sebmarchand): Add support for the PGU (update) phase.
   chrome_pgo_phase = 0
 
-  # Whether or not the official builds should be build with full WPO.
-  full_wpo_on_official = false
+  # Whether or not the official builds should be built with full WPO. Enabled by
+  # default for the PGO and the x64 builds.
+  if (chrome_pgo_phase > 0 || target_cpu == "x64") {
+    full_wpo_on_official = true
+  } else {
+    full_wpo_on_official = false
+  }
 }
 
 declare_args() {
   # Whether to use the gold linker from binutils instead of lld or bfd.
   use_gold = !use_lld && !(is_chromecast && is_linux &&
                            (current_cpu == "arm" || current_cpu == "mipsel")) &&
              ((is_linux && (current_cpu == "x64" || current_cpu == "x86" ||
                             current_cpu == "arm")) ||
               (is_android && (current_cpu == "x86" || current_cpu == "x64" ||
                               current_cpu == "arm")))
@@ skipping 15 matching lines @@
     # Mac and Windows have them separate, so in Release Linux, default them off,
     # but keep them on for Official builds and Chromecast builds.
     symbol_level = 2
   } else if (using_sanitizer) {
     # Sanitizers require symbols for filename suppressions to work.
     symbol_level = 1
   } else {
     symbol_level = 0
   }
 }
-
-# PGO requires full WPO.
-if (chrome_pgo_phase > 0) {
-  full_wpo_on_official = true
-}