WebAssembly: implement the IndexDB caching API

• Component: JavaScriptCore
• Status: RESOLVED CONFIGURATION CHANGED

[JF Bastien]

As described here: https://github.com/WebAssembly/design/blob/master/JS.md#structured-clone-of-a-webassemblymodule

> Structured Clone of a WebAssembly.Module
>
> A WebAssembly.Module is a cloneable object† which means it can be cloned between windows/workers and also stored/retrieved into/from an IDBObjectStore‡. The semantics of a structured clone is as-if the binary source, from which the WebAssembly.Module was compiled, were cloned and recompiled into the target realm. Engines should attempt to share/reuse internal compiled code when performing a structured clone although, in corner cases like CPU upgrade or browser update, this may not be possible and full recompilation may be necessary.
>
> Given the above engine optimizations, structured cloning provides developers explicit control over both compiled-code caching and cross-window/worker code sharing.

─
† https://html.spec.whatwg.org/multipage/infrastructure.html#cloneable-objects
‡ https://w3c.github.io/IndexedDB/#object-store

[Gaurav Dewan]

This can give a great push to startup time as mentioned in
https://bugs.webkit.org/show_bug.cgi?id=178163
For example startup time of webassembly app which takes 2+ sec on Safari 11 on a latest fast mac machine gets loaded from indexeddb in less than 200 milliseconds.

[JF Bastien]

*** Bug 178163 has been marked as a duplicate of this bug. ***

[Sergey Rubanov]

This could be closed per https://github.com/WebAssembly/spec/issues/821

IndexedDB should be replaced by Caching API