Enable /GL for all targets in Official (behind a flag)

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 53 matching lines @@
   # the default.  This is necessary to delay the evaluation of the default
   # value expression until after its input values such as use_gold have
   # been set, e.g. by a toolchain_args() block.
   use_debug_fission = "default"
 
   if (is_win) {
     # Whether the VS xtree header has been patched to disable warning 4702. If
     # it has, then we don't need to disable 4702 (unreachable code warning).
     # The patch is preapplied to the internal toolchain and hence all bots.
     msvs_xtree_patched = false
+
+    # Whether or not the official builds should be build with full WPO.
+    full_wpo_on_official = false
   }
 
   # Omit unwind support in official builds to save space.
   # We can use breakpad for these builds.
   exclude_unwind_tables = is_chrome_branded && is_official_build
 
   # If true, gold linker will save symbol table inside object files.
   # This speeds up gdb startup by 60%
   gdb_index = false
 
@@ skipping 1142 matching lines @@
       # that some libraries aren't needed when they actually are,
       # http://crbug.com/234010. As workaround, disable --as-needed.
       common_optimize_on_ldflags += [ "-Wl,--as-needed" ]
     }
   }
 }
 
 # Default "optimization on" config.
 config("optimize") {
   if (is_win) {
-    # TODO(sebmarchand): Enable this once we've decided to ship with full WPO
-    # and when the change to the incompatible projects (FFmpeg and Yasm) have
-    # have been committed.
-    #if (is_official_build) {
-    #  common_optimize_on_cflags += [ "/GL" ]
-    #}
+    if (is_official_build && full_wpo_on_official) {
+      common_optimize_on_cflags += [ "/GL" ]
+    }
 
     # Favor size over speed, /O1 must be before the common flags. The GYP
     # build also specifies /Os and /GF but these are implied by /O1.
     cflags = [ "/O1" ] + common_optimize_on_cflags + [ "/Oi" ]
   } else if (optimize_for_size) {
     # Favor size over speed.
     cflags = [ "-Os" ] + common_optimize_on_cflags
   } else {
     cflags = [ "-O2" ] + common_optimize_on_cflags
   }
@@ skipping 191 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }