Enable precompiled headers for Blink on Windows

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 4934afae59a08910cd81e04d5c3b44be295f82bb..71da303ec59645a24a3da711fbe504b62d231673 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -1,6 +1,6 @@
 # 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.
+# found in the LICENSE file.
 
 import("//build/config/allocator.gni")
 import("//build/config/chrome_build.gni")
@@ -8,6 +8,7 @@ import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/features.gni")
+import("//build/config/pch.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//build/toolchain/goma.gni")
@@ -31,11 +32,6 @@ declare_args() {
   # of the current object. For iterator- and thread-heavy code, this can
   # significantly slow execution.
   enable_iterator_debugging = true
-
-  # Normally we try to decide whether to use precompiled headers or
-  # not based on the other build arguments, but in some cases it is
-  # easiest to force them off explicitly.
-  disable_precompiled_headers = false
 }
 
 # TODO(brettw) Most of these should be removed. Instead of global feature
@@ -258,7 +254,7 @@ config("feature_flags") {
   }
 }
 
-# Debug/release ----------------------------------------------------------------
+# Debug/release ----------------------------------------------------------------
 
 config("debug") {
   defines = [
@@ -304,7 +300,7 @@ config("release") {
   }
 }
 
-# Default libraries ------------------------------------------------------------
+# Default libraries ------------------------------------------------------------
 
 # This config defines the default libraries applied to all targets.
 config("default_libs") {
@@ -368,7 +364,7 @@ config("default_libs") {
   }
 }
 
-# Executable configs -----------------------------------------------------------
+# Executable configs -----------------------------------------------------------
 
 # Windows linker setup for EXEs and DLLs.
 if (is_win) {
@@ -405,7 +401,7 @@ config("executable_config") {
   }
 }
 
-# Shared library configs -------------------------------------------------------
+# Shared library configs -------------------------------------------------------
 
 # This config defines the configs applied to all shared libraries.
 config("shared_library_config") {
@@ -435,7 +431,7 @@ config("shared_library_config") {
 #
 # Recommend precompiled headers for targets with more than 50 .cc files.
 config("precompiled_headers") {
-  if (!is_official_build && !use_goma && !disable_precompiled_headers) {
+  if (!disable_precompiled_headers) {
     if (is_win) {
       # This is a string rather than a file GN knows about. It has to match
       # exactly what's in the /FI flag below, and what might appear in the