Previously V8 would wrap the WebAssembly.Memory backing stores into
Uint8Arrays and report that as memories, but that's confusing to the
developer, since that's not what's really being used. The way that
DevTools presents the backing stores of memories, it's still perfectly
possible to get hold of an Uint8Array if that's what the developer is
looking for.

To make it possible to easily identify the WebAssembly.Memory objects
in the DevTools front-end (in particular for the memory inspector) we
add a 'webassemblymemory' subtype to the Chrome DevTools Protocol. We
also improve the description for the memories to include the number
of active pages.

Fixed: chromium:1155566
Screenshot: https://imgur.com/8enx57u.png
Change-Id: I63dbabe0e372e9ad6dcc8e6642cdb743147a620c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2574699Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71641}