Electron Releases

Description of Change

Before: V8 keys JS code caches and serialized wasm modules on its version number alone. Release branches cherry-pick V8 fixes as patches without changing that number, so an app that updated between two releases on the same Chromium roll kept deserializing wasm code written by the previous build. When the cherry-pick renumbered builtins (44.3.0 → 44.4.0, cherry-pick-74a4cfde7e.patch, 55 of the 154 wasm jump-table builtins moved by one), the cached code was relinked against the wrong builtins and every previously tiered-up function trapped (RuntimeError: unreachable) or crashed the renderer until the cache was cleared.

After: a code cache or serialized wasm module is only accepted by a build with the same V8 version, the same patches/v8 contents and the same embedded builtins blob; anything else is rejected and recompiled from source.

• patches/v8: new v8_version_hash_salt / v8_version_hash_salt_files GN args mixed into Version::Hash() (JS code cache, CachedDataVersionTag(), wasm header). The files variant is fingerprinted at gn gen time by gni/version_hash_salt.gni with the files as regeneration dependencies, and the salt reaches version.cc through a gen-time header so a change recompiles one file. The serialized wasm module header additionally carries the embedded blob data+code hashes. Both halves are upstreamable.
• build/args/all.gn: v8_version_hash_salt_files = patches/v8/.patches plus every patch it lists.
• patches/chromium/build_allow_electron_to_use_exec_script.patch: allowlist the new gni.

Verified on linux-x64 with a page that instantiateStreamings a module over http and tiers it up:

Checklist

• I have built and tested this change
• I have filled out the PR description
• I have reviewed and verified the changes

Release Notes

Notes: Fixed WebAssembly modules loaded from the code cache crashing or throwing RuntimeError: unreachable after updating between certain patch releases.