Turn on DCHECKs and other debugging code if dcheck_always_on is 1

build/toolchain.gypi

Index: build/toolchain.gypi
diff --git a/build/toolchain.gypi b/build/toolchain.gypi
index 7be54d18cfef06bf90cac7531273ce0ca828c70b..08fd248170b21d5e1e13422f14852ee2c0ab1dd1 100644
--- a/build/toolchain.gypi
+++ b/build/toolchain.gypi
@@ -903,6 +903,9 @@
             },
           }],
         ],
+        'defines': [
+          'ENABLE_SLOW_DCHECKS',
+        ],
       },  # DebugBase0
       # Abstract configuration for v8_optimized_debug == 1.
       'DebugBase1': {
@@ -927,6 +930,9 @@
             'LinkIncremental': '2',
           },
         },
+        'defines': [
+          'ENABLE_SLOW_DCHECKS',
+        ],
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd" or \
             OS=="qnx"', {
@@ -987,9 +993,6 @@
               '-fdata-sections',
               '-ffunction-sections',
             ],
-            'defines': [
-              'OPTIMIZED_DEBUG'
-            ],
             'conditions': [
               # TODO(crbug.com/272548): Avoid -O3 in NaCl
               ['nacl_target_arch=="none"', {