Remove transitional GN code.

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/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 # Because standalone V8 builds are not supported, assume this is part of a
@@ skipping 1519 matching lines @@
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [
     ":internal_config",
     ":features",
     ":toolchain",
   ]
 
   if (!is_debug) {
-    if (using_new_optimization_config) {
-      configs -= [ "//build/config/compiler:default_optimization" ]
-    } else {
-      configs -= [ "//build/config/compiler:optimize" ]
-    }
+    configs -= [ "//build/config/compiler:default_optimization" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 
   defines = []
   deps = [
     ":v8_libbase",
   ]
 
   if (is_win) {
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
@@ skipping 78 matching lines @@
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [
     ":internal_config_base",
     ":features",
     ":toolchain",
   ]
 
   if (!is_debug) {
-    if (using_new_optimization_config) {
-      configs -= [ "//build/config/compiler:default_optimization" ]
-    } else {
-      configs -= [ "//build/config/compiler:optimize" ]
-    }
+    configs -= [ "//build/config/compiler:default_optimization" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 
   defines = []
 
   if (is_posix) {
     sources += [ "src/base/platform/platform-posix.cc" ]
   }
 
   if (is_linux) {
@@ skipping 46 matching lines @@
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [
     ":internal_config_base",
     ":features",
     ":toolchain",
   ]
 
   if (!is_debug) {
-    if (using_new_optimization_config) {
-      configs -= [ "//build/config/compiler:default_optimization" ]
-    } else {
-      configs -= [ "//build/config/compiler:optimize" ]
-    }
+    configs -= [ "//build/config/compiler:default_optimization" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 
   deps = [
     ":v8_libbase",
   ]
 }
 
 ###############################################################################
 # Executables
@@ skipping 136 matching lines @@
     if (!is_component_build) {
       sources += [
         "$target_gen_dir/d8-js.cc",
       ]
     }
     if (v8_enable_i18n_support) {
       deps += [ "//third_party/icu" ]
     }
   }
 }