Add a GN exec_script whitelist.

.gn

 # This file is used by the GN meta build system to find the root of the source
 # tree and to set startup options. For documentation on the values set in this
 # file, run "gn help dotfile" at the command line.
 
 # The location of the build configuration file.
 buildconfig = "//build/config/BUILDCONFIG.gn"
 
 # The secondary source root is a parallel directory tree where
 # GN build files are placed when they can not be placed directly
 # in the source tree, e.g. for third party source trees.
@@ skipping 57 matching lines @@
   "//sync/*",
   "//testing/*",
 
   #"//third_party/*",  # May not ever want this.
   "//tools/*",
 
   #"//ui/*",  # Just a few problems.
   "//url/*",
   "//v8/*",
 ]
+
+# These are the list of GN files that run exec_script. This whitelist exists
+# to force additional review for new uses of exec_script, which is strongly
+# discouraged except for gypi_to_gn calls.
+exec_script_whitelist = [
+  "//ash/BUILD.gn",
+  "//build/config/android/BUILD.gn",
+  "//build/config/android/config.gni",
+  "//build/config/android/internal_rules.gni",
+  "//build/config/android/rules.gni",
+  "//build/config/compiler/BUILD.gn",
+  "//build/config/gcc/gcc_version.gni",
+  "//build/config/ios/ios_sdk.gni",
+  "//build/config/linux/BUILD.gn",
+  "//build/config/linux/pkg_config.gni",
+  "//build/config/mac/mac_sdk.gni",
+  "//build/config/win/visual_studio_version.gni",
+  "//build/gn_helpers.py",
+  "//build/gypi_to_gn.py",
+  "//build/toolchain/gcc_toolchain.gni",
+  "//build/toolchain/mac/BUILD.gn",
+  "//build/toolchain/win/BUILD.gn",
+  "//chrome/android/BUILD.gn",
+  "//chrome/browser/BUILD.gn",
+  "//chrome/browser/chromeos/BUILD.gn",
+  "//chrome/browser/extensions/BUILD.gn",
+  "//chrome/browser/ui/BUILD.gn",
+  "//chrome/chrome_tests.gni",
+  "//chrome/common/BUILD.gn",
+  "//chrome/common/extensions/api/schemas.gni",
+  "//chrome/renderer/BUILD.gn",
+  "//chrome/test/BUILD.gn",
+  "//chrome/utility/BUILD.gn",
+  "//chromeos/BUILD.gn",
+  "//components/domain_reliability/BUILD.gn",
+  "//components/webui_generator/generator/wug.gni",
+  "//content/browser/browser.gni",
+  "//content/child/child.gni",
+  "//content/common/common.gni",
+  "//content/content.gni",
+  "//content/public/android/BUILD.gn",
+  "//content/renderer/renderer.gni",
+  "//content/test/BUILD.gn",
+  "//extensions/common/api/schemas.gni",
+  "//extensions/extensions.gni",
+  "//extensions/shell/app_shell.gni",
+  "//extensions/shell/common/api/schemas.gni",
+  "//google_apis/BUILD.gn",
+  "//gpu/gles2_conform_support/BUILD.gn",
+  "//jingle/BUILD.gn",
+  "//native_client/build/toolchain/gcc_toolchain.gni",
+  "//native_client/build/toolchain/nacl/BUILD.gn",
+  "//native_client/build/config/android/BUILD.gn",
+  "//native_client/build/config/gcc/gcc_version.gni",
+  "//native_client/build/config/ios/ios_sdk.gni",
+  "//native_client/build/config/linux/BUILD.gn",
+  "//native_client/build/config/linux/pkg_config.gni",
+  "//native_client/build/config/mac/mac_sdk.gni",
+  "//native_client/build/config/win/visual_studio_version.gni",
+  "//native_client/build/toolchain/gcc_toolchain.gni",
+  "//native_client/build/toolchain/mac/BUILD.gn",
+  "//native_client/build/toolchain/nacl/BUILD.gn",
+  "//native_client/build/toolchain/win/BUILD.gn",
+  "//net/BUILD.gn",
+  "//ppapi/ppapi_sources.gni",
+  "//printing/BUILD.gn",
+  "//remoting/host/BUILD.gn",
+  "//remoting/remoting_srcs.gni",
+  "//remoting/remoting_version.gni",
+  "//skia/BUILD.gn",
+  "//third_party/android_platform/BUILD.gn",
+  "//third_party/angle/BUILD.gn",
+  "//third_party/boringssl/BUILD.gn",
+  "//third_party/cld_2/BUILD.gn",
+  "//third_party/cython/rules.gni",
+  "//third_party/google_input_tools/inputview.gni",
+  "//third_party/harfbuzz-ng/BUILD.gn",
+  "//third_party/libaddressinput/BUILD.gn",
+  "//third_party/opus/BUILD.gn",
+  "//third_party/WebKit/Source/bindings/bindings.gni",
+  "//third_party/WebKit/Source/bindings/scripts/scripts.gni",
+  "//third_party/WebKit/Source/config.gni",
+  "//third_party/WebKit/Source/core/core.gni",
+  "//third_party/WebKit/Source/devtools/BUILD.gn",
+  "//third_party/WebKit/Source/modules/modules.gni",
+  "//third_party/WebKit/Source/platform/BUILD.gn",
+  "//third_party/WebKit/Source/platform/platform.gni",
+  "//third_party/WebKit/Source/web/BUILD.gn",
+  "//third_party/WebKit/Source/wtf/BUILD.gn",
+  "//tools/gn/BUILD.gn",
+  "//tools/gn/build_settings.h",
+  "//tools/gn/command_help.cc",
+  "//tools/gn/docs/language.md",
+  "//tools/gn/format_test_data/053.gn",
+  "//tools/gn/format_test_data/053.golden",
+  "//tools/gn/format_test_data/055.gn",
+  "//tools/gn/format_test_data/055.golden",
+  "//tools/gn/function_exec_script.cc",
+  "//tools/gn/gn.gyp",
+  "//tools/gn/input_conversion.cc",
+  "//tools/gn/misc/emacs/gn.el",
+  "//tools/gn/misc/vim/syntax/gn.vim",
+  "//tools/gn/setup.cc",
+  "//ui/views/BUILD.gn",
+]