Add precompiled headers to GN build for large targets.

content/browser/BUILD.gn

 # Copyright 2014 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/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//content/browser/browser.gni")
 import("//media/media_options.gni")
 
 source_set("browser") {
   # Only the public target should depend on this. All other targets (even
   # internal content ones) should depend on the public one.
   visibility = [ "//content/public/browser:browser_sources" ]
 
+  configs += [ "//build/config:precompiled_headers" ]
   defines = []
   libs = []
   ldflags = []
 
   # Shared deps. See also non-iOS deps below.
   deps = [
     "//base",
     "//base:base_static",
     "//components/mime_util",
     "//content:resources",
@@ skipping 475 matching lines @@
   if (enable_webvr) {
     sources += [
       "vr/vr_device.cc",
       "vr/vr_device.h",
       "vr/vr_device_manager.cc",
       "vr/vr_device_manager.h",
       "vr/vr_device_provider.h",
     ]
   }
 }