Update post-mortem metadata generation

Update post-mortem metadata generation

mdb_v8, a post-mortem debugger for Node.js, now uses JSArrayBuffer's
backing_store property and JSArrayBufferView's byte_offset property to
get access to the content of Buffer instances in node (which are
Uint8Array instances). This change adds post-mortem metadata for these
two properties.

This change also fixes a typo in
inobject_properties_of_constructor_function_index_offset that was added
to gen-postmortem-metadata in a previous change. It should be named
inobject_properties_or_constructor_function_index instead.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1363403003

Cr-Commit-Position: refs/heads/master@{#30926}