Add use_rtti flag to control Run-Time Type Identification

build/config/BUILDCONFIG.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.
 
 # =============================================================================
 # WHAT IS THIS FILE?
 # =============================================================================
 #
 # This is the master GN build configuration. This file is loaded after the
 # build args (args.gn) for the build directory and after the toplevel ".gn"
@@ skipping 144 matching lines @@
 }
 
 declare_args() {
   # Component build. Setting to true compiles targets declared as "components"
   # as shared libraries loaded dynamically. This speeds up development time.
   # When false, components will be linked statically.
   #
   # For more information see
   # https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md
   is_component_build = is_debug && current_os != "ios"
+
+  # Run-Time Type Identification.
+  use_rtti = false

[kjellander_chromium, 2017/01/02 07:47:14]

Let me know if there's a better place to put this.

 }
 
 assert(!(is_debug && is_official_build), "Can't do official debug builds")
 
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
 #
 # Here we set the default toolchain, as well as the variable host_toolchain
 # which will identify the toolchain corresponding to the local system when
@@ skipping 298 matching lines @@
   "//build/config/compiler:compiler",
   "//build/config/compiler:pthread",
   "//build/config/compiler:clang_stackrealign",
   "//build/config/compiler:compiler_arm_fpu",
   "//build/config/compiler:compiler_arm_thumb",
   "//build/config/compiler:chromium_code",
   "//build/config/compiler:default_include_dirs",
   "//build/config/compiler:default_optimization",
   "//build/config/compiler:default_stack_frames",
   "//build/config/compiler:default_symbols",
-  "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",
   "//build/config/sanitizers:default_sanitizer_flags",
 ]
+if (use_rtti) {
+  default_compiler_configs += [ "//build/config/compiler:rtti" ]
+} else {
+  default_compiler_configs += [ "//build/config/compiler:no_rtti" ]
+}
 if (is_win) {
   default_compiler_configs += [
     "//build/config/win:default_crt",
     "//build/config/win:lean_and_mean",
     "//build/config/win:nominmax",
     "//build/config/win:unicode",
     "//build/config/win:winver",
     "//build/config/win:vs_code_analysis",
   ]
 }
@@ skipping 149 matching lines @@
 set_defaults("component") {
   if (is_component_build) {
     configs = default_shared_library_configs
     if (is_android) {
       configs -= [ "//build/config/android:hide_native_jni_exports" ]
     }
   } else {
     configs = default_compiler_configs
   }
 }