Add support for Dr memory in the GN build.

build/config/BUILD.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.
 
 declare_args() {
-  # When set, turns off the definition of _GLIBCXX_DEBUG when it would
-  # otherwise be set. Setting _GLIBCXX_DEBUG adds iterator debugging stuff
-  # that is usually helpful in debugging, but can cause problems in some
-  # contexts.
-  disable_glibcxx_debug = false
+  # When set, turns off the (normally-on) iterator debugging and related stuff
+  # that is normall turned on for Debug builds. These are generally useful for

[scottmg, 2014/01/17 23:52:25]

normally

+  # catching bugs but in some cases may cause conflicts or excessive slowness.
+  disable_iterator_debugging = false
 }
 
 config("my_msvs") {
   defines = [
       "CHROMIUM_BUILD",
       "TOOLKIT_VIEWS=1",
       "USE_LIBJPEG_TURBO=1",
       "ENABLE_ONE_CLICK_SIGNIN",
       "ENABLE_REMOTING=1",
       "ENABLE_WEBRTC=1",
@@ skipping 18 matching lines @@
       "ENABLE_SETTINGS_APP=1",
       "ENABLE_MANAGED_USERS=1",
   ]
 
   if (use_aura) {
     defines += [ "USE_AURA=1" ]
   }
 }
 
 config("feature_flags") {
-  #defines = 
 }
 
 config("debug") {
   defines = [
     "_DEBUG",
     "DYNAMIC_ANNOTATIONS_ENABLED=1",
     "WTF_USE_DYNAMIC_ANNOTATIONS=1",
   ]
 
-  if (is_linux && !is_android && cpu_arch == "x64" && !disable_glibcxx_debug) {
+  if (is_win) {
+    if (disable_iterator_debugging) {
+      # Iterator debugging is enabled by the compiler on debug builds, and we
+      # have to tell it to turn it off.
+      defines += [ "_HAS_ITERATOR_DEBUGGING=0" ]
+    }
+  } else if (is_linux && !is_android && cpu_arch == "x64" &&
+             !disable_iterator_debugging) {
     # Enable libstdc++ debugging facilities to help catch problems early, see
     # http://crbug.com/65151 .
     # TODO(phajdan.jr): Should we enable this for all of POSIX?
     defines += [ "_GLIBCXX_DEBUG=1" ]
   }
 }
 
 config("release") {
 
 }