Move `gn check` into the `generate_build_files` step.

.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.
 secondary_source = "//build/secondary/"
 
 # These are the targets to check headers for by default. The files in targets
 # matching these patterns (see "gn help label_pattern" for format) will have
 # their includes checked for proper dependencies when you run either
 # "gn check" or "gn gen --check".
 check_targets = [
   #"//apps/*",  # Medium-hard.
   #"//ash/*",  # Medium-hard.
   #"//base/*",  # Needs GN binary changes to work on Android.
   "//blink/*",
   "//breakpad/*",
   "//build/*",
   "//cc/*",
 
   #"//chrome/*",  # Epic number of errors.
-  "//chrome/installer/*",
+  #"//chrome/installer/*", # A few errors, need to verify the size after fixing.
   "//chromecast/*",
 
   # TODO(brettw): Fix http://crbug.com/460828 and uncomment the following
   # line.
   #"//chrome_elf/*",
   "//cloud_print/*",
 
   #"//components/*",  # Lots of errors.
   "//components/app_modal/*",
   "//components/autofill/*",
   "//components/bookmarks/*",
   "//components/google/*",
   "//components/history/*",
-  "//components/html_viewer/*",
+
+  # TODO(dpranke): Reenable once v8 exports v8_base as a public_dep
+  #"//components/html_viewer/*",
+
   "//components/mus/*",
   "//components/omnibox/*",
   "//components/os_crypt/*",
   "//components/pref_registry/*",
   "//components/undo/*",
   "//components/update_client/*",
   "//components/url_formatter/*",
   "//components/url_matcher/*",
   "//components/user_manager/*",
   "//components/user_prefs/*",
@@ skipping 156 matching lines @@
   "//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/accessibility/BUILD.gn",
   "//ui/views/BUILD.gn",
 ]