Revert of Content "gn check" work.

.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/installer/*",
   "//chrome/third_party/mozilla_security_manager/*",
   "//chrome/tools/*",
   "//chrome/utility/*",
   "//chromecast/*",
   "//chrome_elf/*",
   "//cloud_print/*",
   "//components/*",
 
   #"//content/*",  # A whole lot of errors.
-  "//content/gpu/*",
-  "//content/plugin/*",
   "//content/public/*",
   "//content/renderer/*",
-
-  #"//content/shell/*",  # Needs Android fix, bug 597020.
-
-  #"//content/test/*",  # A couple of errors left.
-  "//content/test:content_gl_benchmark",
-  "//content/test:content_gl_tests",
-  "//content/test:content_perftests",
-  "//content/test:content_site_isolation_browsertests",
-  "//content/test:content_test_mojo_bindings",
-  "//content/test:content_unittests",
-  "//content/test:test_support",
   "//courgette/*",
   "//crypto/*",
   "//data/*",
   "//dbus/*",
   "//device/*",
 
   #"//extensions/*",  # Lots of errors.
   "//gin/*",
   "//google_apis/*",
   "//google_update/*",
@@ skipping 176 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",
 ]