Enable full WPO for the PGO 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")
 
 declare_args() {
   # How many symbols to include in the build. This affects the performance of
   # the build since the symbols are large and dealing with them is slow.
   #   2 means regular build with symbols.
   #   1 means minimal symbols, usually enough for backtraces only.
   #   0 means no symbols.
   #   -1 means auto-set according to debug/release and platform.
   symbol_level = -1
 
   # Compile in such a way as to enable profiling of the generated code. For
   # example, don't omit the frame pointer and leave in symbols.
   enable_profiling = false
 
+  # 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
 }
 
 # If it wasn't manually set, set to an appropriate default.
 assert(symbol_level >= -1 && symbol_level <= 2, "Invalid symbol_level")
 if (symbol_level == -1) {
   if (is_android && use_order_profiling) {
     # With instrumentation enabled, debug info puts libchrome.so over 4gb, which
     # causes the linker to produce an invalid ELF. http://crbug.com/574476
     symbol_level = 0
   } else if (is_win && is_clang && !using_sanitizer) {
     # TODO(thakis): Remove this again once building with clang/win and
     # debug info doesn't make link.exe run for hours.
     symbol_level = 1
   } else if (!is_linux || is_debug || is_official_build || is_chromecast) {
     # Linux is slowed by having symbols as part of the target binary, whereas
     # 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
+}