Remove the deprecated use_nss and USE_NSS flags.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index aa2d8d7a6a3287fe6f8fbd3f49e622ce1591cec4..bf90a86898ba45f68a2401c059dcc8b222933eb5 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -683,14 +683,8 @@
         # NSS usage.
         ['(OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris") and use_openssl==0', {
           'use_nss_certs%': 1,
-          # TODO(davidben): use_nss is deprecated and will be removed. See
-          # https://crbug.com/462040.
-          'use_nss%': 1,
         }, {
           'use_nss_certs%': 0,
-          # TODO(davidben): use_nss is deprecated and will be removed. See
-          # https://crbug.com/462040.
-          'use_nss%': 0,
         }],
 
         # When OpenSSL is used for SSL and crypto on Unix-like systems, use
@@ -1091,7 +1085,6 @@
     'use_libpci%': '<(use_libpci)',
     'use_openssl%': '<(use_openssl)',
     'use_openssl_certs%': '<(use_openssl_certs)',
-    'use_nss%': '<(use_nss)',
     'use_nss_certs%': '<(use_nss_certs)',
     'use_udev%': '<(use_udev)',
     'os_bsd%': '<(os_bsd)',
@@ -3005,12 +2998,7 @@
         'defines': ['USE_GLIB=1'],
       }],
       ['<(use_nss_certs)==1 and >(nacl_untrusted_build)==0', {
-        'defines': [
-          'USE_NSS_CERTS=1',
-          # TODO(davidben): USE_NSS is a deprecated alias for USE_NSS_CERTS and
-          # will be removed. See https://crbug.com/462040.
-          'USE_NSS=1',
-        ],
+        'defines': ['USE_NSS_CERTS=1'],
       }],
       ['<(chromeos)==1 and >(nacl_untrusted_build)==0', {
         'defines': ['OS_CHROMEOS=1'],