Enable WPO for the x64 Official builds.

build/config/compiler/compiler.gni

Index: build/config/compiler/compiler.gni
diff --git a/build/config/compiler/compiler.gni b/build/config/compiler/compiler.gni
index 13109c28639bf43b10415136942e174fefad33b3..98f99f2298c5640c43e344d59e33a9b91639925b 100644
--- a/build/config/compiler/compiler.gni
+++ b/build/config/compiler/compiler.gni
@@ -30,8 +30,13 @@ declare_args() {
   # 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() {
@@ -67,8 +72,3 @@ if (symbol_level == -1) {
     symbol_level = 0
   }
 }
-
-# PGO requires full WPO.
-if (chrome_pgo_phase > 0) {
-  full_wpo_on_official = true
-}