Introduce a gyp variable to control whether or not slow dchecks are on

build/toolchain.gypi

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 865 matching lines @@
                 'RuntimeLibrary': '3',  # /MDd
               }, {
                 'RuntimeLibrary': '1',  # /MTd
               }],
             ],
           },
           'VCLinkerTool': {
             'LinkIncremental': '2',
           },
         },
+        'variables': {
+          'v8_enable_slow_dchecks%': 1,
+        },
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd" or \
             OS=="qnx"', {
             'cflags!': [
               '-O3',
               '-O2',
               '-O1',
               '-Os',
             ],
             'cflags': [
               '-fdata-sections',
               '-ffunction-sections',
             ],
           }],
           ['OS=="mac"', {
             'xcode_settings': {
                'GCC_OPTIMIZATION_LEVEL': '0',  # -O0
             },
           }],
-        ],
-        'defines': [
-          'ENABLE_SLOW_DCHECKS',
+          ['v8_enable_slow_dchecks==1', {
+            'defines': [
+              'ENABLE_SLOW_DCHECKS',
+            ],
+          }],
         ],
       },  # DebugBase0
       # Abstract configuration for v8_optimized_debug == 1.
       'DebugBase1': {
         'abstract': 1,
         'msvs_settings': {
           'VCCLCompilerTool': {
             'Optimization': '1',
             'InlineFunctionExpansion': '2',
             'EnableIntrinsicFunctions': 'true',
             'FavorSizeOrSpeed': '0',
             'StringPooling': 'true',
             'BasicRuntimeChecks': '0',
             'conditions': [
               ['component=="shared_library"', {
                 'RuntimeLibrary': '3',  # /MDd
               }, {
                 'RuntimeLibrary': '1',  # /MTd
               }],
             ],
           },
           'VCLinkerTool': {
             'LinkIncremental': '2',
           },
         },
-        'defines': [
-          'ENABLE_SLOW_DCHECKS',
-        ],
+        'variables': {
+          'v8_enable_slow_dchecks%': 1,
+        },
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd" or \
             OS=="qnx"', {
             'cflags!': [
               '-O0',
               '-O3', # TODO(2807) should be -O1.
               '-O2',
               '-Os',
             ],
             'cflags': [
               '-fdata-sections',
               '-ffunction-sections',
               '-O1', # TODO(2807) should be -O3.
             ],
           }],
           ['OS=="mac"', {
             'xcode_settings': {
                'GCC_OPTIMIZATION_LEVEL': '3',  # -O3
                'GCC_STRICT_ALIASING': 'YES',
             },
           }],
+          ['v8_enable_slow_dchecks==1', {
+            'defines': [
+              'ENABLE_SLOW_DCHECKS',
+            ],
+          }],
         ],
       },  # DebugBase1
       # Abstract configuration for v8_optimized_debug == 2.
       'DebugBase2': {
         'abstract': 1,
         'msvs_settings': {
           'VCCLCompilerTool': {
             'Optimization': '2',
             'InlineFunctionExpansion': '2',
             'EnableIntrinsicFunctions': 'true',
             'FavorSizeOrSpeed': '0',
             'StringPooling': 'true',
             'BasicRuntimeChecks': '0',
             'conditions': [
               ['component=="shared_library"', {
                 'RuntimeLibrary': '3',  #/MDd
               }, {
                 'RuntimeLibrary': '1',  #/MTd
               }],
             ],
           },
           'VCLinkerTool': {
             'LinkIncremental': '1',
             'OptimizeReferences': '2',
             'EnableCOMDATFolding': '2',
           },
         },
+        'variables': {
+          'v8_enable_slow_dchecks%': 0,
+        },
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd" or \
             OS=="qnx"', {
             'cflags!': [
               '-O0',
               '-O1',
               '-Os',
             ],
             'cflags': [
               '-fdata-sections',
               '-ffunction-sections',
             ],
             'conditions': [
               # TODO(crbug.com/272548): Avoid -O3 in NaCl
               ['nacl_target_arch=="none"', {
                 'cflags': ['-O3'],
                 'cflags!': ['-O2'],
                 }, {
                 'cflags': ['-O2'],
                 'cflags!': ['-O3'],
               }],
             ],
           }],
           ['OS=="mac"', {
             'xcode_settings': {
               'GCC_OPTIMIZATION_LEVEL': '3',  # -O3
               'GCC_STRICT_ALIASING': 'YES',
             },
           }],
+          ['v8_enable_slow_dchecks==1', {
+            'defines': [
+              'ENABLE_SLOW_DCHECKS',
+            ],
+          }],
         ],
       },  # DebugBase2
       # Common settings for the Debug configuration.
       'DebugBaseCommon': {
         'abstract': 1,
         'defines': [
           'ENABLE_DISASSEMBLER',
           'V8_ENABLE_CHECKS',
           'OBJECT_PRINT',
           'VERIFY_HEAP',
@@ skipping 34 matching lines @@
           }],
           ['v8_optimized_debug==1', {
             'inherit_from': ['DebugBase1'],
           }],
           ['v8_optimized_debug==2', {
             'inherit_from': ['DebugBase2'],
           }],
         ],
       },  # Debug
       'Release': {
+        'variables': {
+          'v8_enable_slow_dchecks%': 0,
+        },
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd"', {
             'cflags!': [
               '-Os',
             ],
             'cflags': [
               '-fdata-sections',
               '-ffunction-sections',
               '<(wno_array_bounds)',
             ],
@@ skipping 46 matching lines @@
                   }],
                 ],
               },
               'VCLinkerTool': {
                 'LinkIncremental': '1',
                 'OptimizeReferences': '2',
                 'EnableCOMDATFolding': '2',
               },
             },
           }],  # OS=="win"
+          ['v8_enable_slow_dchecks==1', {
+            'defines': [
+              'ENABLE_SLOW_DCHECKS',
+            ],
+          }],
         ],  # conditions
       },  # Release
     },  # configurations
   },  # target_defaults
 }