Update postmortem metadata generation script

See: https://github.com/nodejs/node-v8/pull/84
Change-Id: Ia1d4b110367c795e952e8e3d0a067f601a306077
Reviewed-on: https://chromium-review.googlesource.com/c/1278014
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56781}

tools/gen-postmortem-metadata.py

@@ -250,7 +250,9 @@ extras_accessors = [
     'FixedArray, data, uintptr_t, kHeaderSize',
     'FixedTypedArrayBase, external_pointer, Object, kExternalPointerOffset',
     'JSArrayBuffer, backing_store, Object, kBackingStoreOffset',
-    'JSArrayBufferView, byte_offset, Object, kByteOffsetOffset',
+    'JSArrayBuffer, byte_length, size_t, kByteLengthOffset',
+    'JSArrayBufferView, byte_length, size_t, kByteLengthOffset',
+    'JSArrayBufferView, byte_offset, size_t, kByteOffsetOffset',
     'JSTypedArray, length, Object, kLengthOffset',
     'Map, instance_size_in_words, char, kInstanceSizeInWordsOffset',
     'Map, inobject_properties_start_or_constructor_function_index, char, kInObjectPropertiesStartOrConstructorFunctionIndexOffset',
@@ -275,6 +277,7 @@ extras_accessors = [
     'SlicedString, parent, String, kParentOffset',
     'Code, instruction_start, uintptr_t, kHeaderSize',
     'Code, instruction_size, int, kInstructionSizeOffset',
+    'String, length, int32_t, kLengthOffset',
 ];
 
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