Remove "extra checks"

build/features.gypi

Index: build/features.gypi
diff --git a/build/features.gypi b/build/features.gypi
index 25041ce42fde0b4f964e9f50f31c85b2cafb7cde..a3ee0fbbf08cd52e768984be9403ad8426c7eff3 100644
--- a/build/features.gypi
+++ b/build/features.gypi
@@ -102,13 +102,9 @@
       'DebugBaseCommon': {
         'abstract': 1,
         'variables': {
-          'v8_enable_extra_checks%': 1,
           'v8_enable_handle_zapping%': 1,
         },
         'conditions': [
-          ['v8_enable_extra_checks==1', {
-            'defines': ['ENABLE_EXTRA_CHECKS',],
-          }],
           ['v8_enable_handle_zapping==1', {
             'defines': ['ENABLE_HANDLE_ZAPPING',],
           }],
@@ -116,13 +112,9 @@
       },  # Debug
       'Release': {
         'variables': {
-          'v8_enable_extra_checks%': 0,
           'v8_enable_handle_zapping%': 1,
         },
         'conditions': [
-          ['v8_enable_extra_checks==1', {
-            'defines': ['ENABLE_EXTRA_CHECKS',],
-          }],
           ['v8_enable_handle_zapping==1', {
             'defines': ['ENABLE_HANDLE_ZAPPING',],
           }],