Add JSTypedArray's length in post-mortem metadata.

tools/gen-postmortem-metadata.py

 #!/usr/bin/env python
 
 #
 # Copyright 2012 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.
@@ skipping 132 matching lines @@
         'value': 'ScopeInfo::kVariablePartIndex' },
 ];
 
 #
 # The following useful fields are missing accessors, so we define fake ones.
 #
 extras_accessors = [
     'HeapObject, map, Map, kMapOffset',
     'JSObject, elements, Object, kElementsOffset',
     'FixedArray, data, uintptr_t, kHeaderSize',
+    'JSTypedArray, length, Object, kLengthOffset',
     'Map, instance_attributes, int, kInstanceAttributesOffset',
     'Map, inobject_properties_of_constructor_function_index_offset, int, kInObjectPropertiesOrConstructorFunctionIndexOffset',
     'Map, instance_size, int, kInstanceSizeOffset',
     'Map, bit_field, char, kBitFieldOffset',
     'Map, bit_field2, char, kBitField2Offset',
     'Map, bit_field3, int, kBitField3Offset',
     'Map, prototype, Object, kPrototypeOffset',
     'NameDictionaryShape, prefix_size, int, kPrefixSize',
     'NameDictionaryShape, entry_size, int, kEntrySize',
     'SeededNumberDictionaryShape, prefix_size, int, kPrefixSize',
@@ skipping 369 matching lines @@
 
         out.write(footer);
 
 if (len(sys.argv) < 4):
         print('usage: %s output.cc objects.h objects-inl.h' % sys.argv[0]);
         sys.exit(2);
 
 load_objects();
 load_fields();
 emit_config();