Add a new flag to assist in landing optimization update.

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.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 160 matching lines @@
 # to be global.
 #
 # In the new scheme, this file sets a "default_symbols" and
 # "default_optimization" configs, which then expands to the right thing
 # depending on the current build. This means less information has to be global,
 # and there's only one config to remove that's the same in all cases for
 # targets that want to override it. It also means that the associated flags can
 # be non-global.
 using_new_global_compiler_configs = false
 
+# To assist in a multi-sided landing of updating the default optimization
+# config. When false, this file sets up the default optimization config to be
+# either "no_optimize" (debug) or "optimize" (release). When true it will
+# always set the config "default_optimization".
+#
+# TODO(brettw) remove this when all repos are updated.
+using_new_optimization_config = false
+
 # =============================================================================
 # OS DEFINITIONS
 # =============================================================================
 #
 # We set these various is_FOO booleans for convenience in writing OS-based
 # conditions.
 #
 # - is_android, is_chromeos, is_ios, and is_win should be obvious.
 # - is_mac is set only for desktop Mac. It is not set on iOS.
 # - is_posix is true for mac and any Unix-like system (basically everything
@@ skipping 450 matching lines @@
     forward_variables_from(invoker, "*")
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     if (!defined(deps)) {
       deps = []
     }
     deps += [ "//build/config/sanitizers:deps" ]
   }
 }