Whitelist all of content for "gn check"

.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 18 matching lines @@
   "//chrome/common/*",
   "//chrome/installer/*",
   "//chrome/third_party/mozilla_security_manager/*",
   "//chrome/tools/*",
   "//chrome/utility/*",
   "//chromecast/*",
   "//chromeos/*",
   "//chrome_elf/*",
   "//cloud_print/*",
   "//components/*",
-
-  #"//content/*",  # Enable when the individual ones below are done.
-  #"//content/app/*",
-  "//content/browser/*",
-  "//content/child/*",
-  "//content/common/*",
-  "//content/gpu/*",
-  "//content/ppapi_plugin/*",
-  "//content/public/*",
-  "//content/renderer/*",
-  "//content/shell/*",
-  "//content/test/*",
-
-  #"//content/utility/*",
-  #"//content/zygote/*",
-
-  "//content/test:content_perftests",
-  "//content/test:content_site_isolation_browsertests",
-  "//content/test:content_test_mojo_bindings",
-  "//content/test:content_unittests",
-  "//content/test:test_support",
-  "//content/utility/*",
+  "//content/*",
   "//courgette/*",
   "//crypto/*",
   "//data/*",
   "//dbus/*",
   "//device/*",
 
   #"//extensions/*",  # Lots of errors.
   "//gin/*",
   "//google_apis/*",
   "//google_update/*",
@@ skipping 262 matching lines @@
   "//tools/gn/misc/emacs/gn.el",
   "//tools/gn/misc/vim/syntax/gn.vim",
   "//tools/gn/setup.cc",
   "//ui/accessibility/BUILD.gn",
   "//ui/gfx/BUILD.gn",
   "//ui/views/BUILD.gn",
   "//ui/views/mus/BUILD.gn",
   "//v8/test/cctest/BUILD.gn",
   "//v8/test/unittests/BUILD.gn",
 ]