Optionally use new scheme for optimization configs.

Source/core/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/chrome_build.gni")
 import("//build/config/ui.gni")
 import("//third_party/WebKit/Source/bindings/bindings.gni")
 import("//third_party/WebKit/Source/bindings/core/v8/generated.gni")
 import("//third_party/WebKit/Source/bindings/modules/modules.gni")
 import("//third_party/WebKit/Source/bindings/modules/v8/generated.gni")
 import("//third_party/WebKit/Source/bindings/scripts/scripts.gni")
 import("//third_party/WebKit/Source/config.gni")
 import("//third_party/WebKit/Source/core/core.gni")
 import("//third_party/WebKit/Source/build/scripts/scripts.gni")
 import("//third_party/WebKit/Source/platform/platform_generated.gni")
 
 visibility = [ "//third_party/WebKit/Source/*" ]
 
 rel_blink_core_gen_dir = rebase_path(blink_core_output_dir, root_build_dir)
 
 # Compute the optimization level. The GYP code sets "optimize: max" which sets
 # speed-over-size optimization for official builds on Windows only. The GN's
 # build optimize_max config applies this optimization on all platforms, so
 # compute how to modify the config list to duplicate the GYP behavior.
-if (is_debug) {
-  core_config_remove = [ "//build/config/compiler:no_optimize" ]
-  core_config_add = core_config_remove  # NOP
+if (is_debug || !is_win || !is_official_build) {
+  # NOP.
+  core_config_add = []
+  core_config_remove = []
 } else {
-  core_config_remove = [ "//build/config/compiler:optimize" ]
-
-  if (is_win && is_official_build) {
-    core_config_add = [ "//build/config/compiler:optimize_max" ]
+  if (using_new_global_compiler_configs) {
+    # GN build is moving to a single default optimization config that prevents
+    # us from having to break out the debug/release conditions to override.
+    core_config_remove = [ "//build/config/compiler:default_optimization" ]
   } else {
-    core_config_add = core_config_remove  # NOP
+    core_config_remove = [ "//build/config/compiler:optimize" ]
   }
+  core_config_add = [ "//build/config/compiler:optimize_max" ]
 }
 
 # Core targets also get wexit time destructors.
 core_config_add += [ "//build/config/compiler:wexit_time_destructors" ]
 
 config("core_include_dirs") {
   include_dirs = [
     "..",
     "$root_gen_dir/blink",
   ]
@@ skipping 992 matching lines @@
     "$blink_core_output_dir/{{source_name_part}}.h",
   ]
   args = [
     "{{source}}",
     rel_blink_core_gen_dir,
     bison_exe,
   ]
 
   deps = make_core_generated_deps
 }