Enable compiling GN by default.

build/all.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'All',
       'type': 'none',
       'xcode_create_dependents_test_runner': 1,
@@ skipping 44 matching lines @@
             '../third_party/libwebp/libwebp.gyp:*',
             '../third_party/libxslt/libxslt.gyp:*',
             '../third_party/lzma_sdk/lzma_sdk.gyp:*',
             '../third_party/mesa/mesa.gyp:*',
             '../third_party/modp_b64/modp_b64.gyp:*',
             '../third_party/npapi/npapi.gyp:*',
             '../third_party/ots/ots.gyp:*',
             '../third_party/qcms/qcms.gyp:*',
             '../third_party/re2/re2.gyp:re2',
             '../third_party/WebKit/public/all.gyp:*',
+            '../tools/gn/gn.gyp:*',
             '../tools/perf/clear_system_cache/clear_system_cache.gyp:*',
             '../v8/tools/gyp/v8.gyp:*',
             '../webkit/glue/webkit_glue.gyp:*',
             '../webkit/renderer/compositor_bindings/compositor_bindings_tests.gyp:*',
             '<(libjpeg_gyp_path):*',
           ],
         }, { #  'OS=="ios"'
           'dependencies': [
             '../ios/ios.gyp:*',
           ],
@@ skipping 839 matching lines @@
             '../chrome/chrome.gyp:interactive_ui_tests_run',
             '../chrome/chrome.gyp:sync_integration_tests_run',
             '../chrome/chrome.gyp:unit_tests_run',
             '../net/net.gyp:net_unittests_run',
           ],
         }, # target_name: chromium_swarm_tests
       ],
     }],
   ], # conditions
 }