[post-mortem] JS_API_OBJECT_TYPE and friends

Export JS_API_OBJECT_TYPE, JS_SPECIAL_API_OBJECT_TYPE.

Exports JSObject::kHeaderSize to ease the inspection of internal fields
in llnode.

BUG=
R=machenbach

Review-Url: https://codereview.chromium.org/2514063002
Cr-Commit-Position: refs/heads/master@{#41157}

tools/gen-postmortem-metadata.py

@@ -55,6 +55,8 @@ import sys
 #
 consts_misc = [
     { 'name': 'FirstNonstringType',     'value': 'FIRST_NONSTRING_TYPE' },
+    { 'name': 'APIObjectType',          'value': 'JS_API_OBJECT_TYPE' },
+    { 'name': 'SpecialAPIObjectType',   'value': 'JS_SPECIAL_API_OBJECT_TYPE' },
 
     { 'name': 'IsNotStringMask',        'value': 'kIsNotStringMask' },
     { 'name': 'StringTag',              'value': 'kStringTag' },
@@ -225,6 +227,7 @@ extras_accessors = [
     'JSFunction, context, Context, kContextOffset',
     'HeapObject, map, Map, kMapOffset',
     'JSObject, elements, Object, kElementsOffset',
+    'JSObject, internal_fields, uintptr_t, kHeaderSize',
     'FixedArray, data, uintptr_t, kHeaderSize',
     'JSArrayBuffer, backing_store, Object, kBackingStoreOffset',
     'JSArrayBufferView, byte_offset, Object, kByteOffsetOffset',