Removed unused mojo_nacl code and GYP targets.

There are subtle generated dependency issues breaking
several bots. The code is upstream in the Mojo repo
at this point and we have no need for the GYP targets
in the foreseeable future.

BUG=519643
TBR=jam@chromium.org

Review URL: https://codereview.chromium.org/1279133006

Cr-Commit-Position: refs/heads/master@{#342920}

build/all.gyp

@@ -494,14 +494,6 @@
             '../components/nacl.gyp:nacl_helper_nonsfi_unittests',
           ],
         }],
-        ['disable_nacl==0 and disable_nacl_untrusted==0', {
-          'dependencies': [
-            '../mojo/mojo_nacl_untrusted.gyp:libmojo',
-            '../mojo/mojo_nacl.gyp:monacl_codegen',
-            '../mojo/mojo_nacl.gyp:monacl_sel',
-            '../mojo/mojo_nacl.gyp:monacl_shell',
-          ],
-        }],
       ],
     }, # target_name: chromium_builder_tests
   ],

build/gn_migration.gypi

@@ -12,9 +12,6 @@
 # type 'ninja gyp_all' and then 'ninja all', the second build should do
 # nothing. 'gyp_all' should just depend on the other four targets.
 #
-# 'gyp_only' lists any targets that are not meant to be ported over to the GN
-# build.
-#
 # 'gyp_remaining' lists all of the targets that still need to be converted,
 # i.e., all of the other (non-empty) targets that a GYP build will build.
 #
@@ -28,7 +25,6 @@
       'type': 'none',
       'dependencies': [
         'both_gn_and_gyp',
-        'gyp_only',
         'gyp_remaining',
       ]
     },
@@ -489,21 +485,6 @@
         }],
       ],
     },
-    {
-      'target_name': 'gyp_only',
-      'type': 'none',
-      'conditions': [
-        ['OS=="linux" or OS=="win"', {
-          'conditions': [
-            ['disable_nacl==0 and disable_nacl_untrusted==0', {
-              'dependencies': [
-                '../mojo/mojo_nacl.gyp:monacl_shell',  # This should not be built in chromium.
-              ]
-            }],
-          ]
-        }],
-      ],
-    },
     {
       'target_name': 'gyp_remaining',
       'type': 'none',