Add JavaScriptCore as a third-party optional download to DEPS

Add the javascript shell WebKit JavaScriptCore as an optional
download in third_party/jsc. This is a CIPD download, and includes
an update.sh script to upload a new version of jsc to CIPD and
update DEPS.

Bug: b/322134579
Change-Id: I94902ccdff3d121e5be51ef6eeab595fc24ad7e3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/348161
Commit-Queue: William Hesse <whesse@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>

DEPS

@@ -72,6 +72,7 @@ vars = {
   "checkout_javascript_engines": False,
   "d8_tag": "version:12.1.131",
   "jsshell_tag": "version:120.0",
+  "jsc_tag": "version:273394",
 
   # https://chrome-infra-packages.appspot.com/p/fuchsia/third_party/clang
   "clang_version": "git_revision:b3a9e8f7c0afb00147ab6c6a6ad426de149420dd",
@@ -251,6 +252,14 @@ deps = {
       "condition": "checkout_javascript_engines",
       "dep_type": "cipd",
   },
+  Var("dart_root") + "/third_party/jsc": {
+      "packages": [{
+          "package": "dart/third_party/jsc/linux-amd64",
+          "version": Var("jsc_tag"),
+      }],
+      "condition": "checkout_javascript_engines and host_os == 'linux' and host_cpu == 'x64'",
+      "dep_type": "cipd",
+  },
   Var("dart_root") + "/third_party/devtools": {
       "packages": [{
           "package": "dart/third_party/flutter/devtools",

third_party/jsc/README.google

@@ -0,0 +1,11 @@
+Name: The WebKit JavaScriptCore shell.
+Short Name: jsc
+URL: https://webkitgtk.org/jsc-built-products/x86_64/release/
+Version: 273394@main
+Date: January 24, 2024
+License: GPL-2.0, https://opensource.org/license/gpl-2-0/
+
+Description:
+This directory contains the Webkit JavaScriptCore shell binaries.
+
+The binaries are used for testing dart code compiled to javascript.

third_party/jsc/update.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Uploads a new version of the checked in jsc CIPD packages
+# jsc is the JavaScriptCore shell from WebKit.
+#
+# Only the latest builds for the last few days are available
+# for download. They are indexed by build number.
+# This script only downloads the latest build, and uploads
+# it to CIPD with the build number as the version tag.
+# It updates DEPS to download that version of jsc from CIPD.
+set -ex
+
+tmpdir=$(mktemp -d)
+cleanup() {
+  rm -rf "$tmpdir"
+}
+trap cleanup EXIT HUP INT QUIT TERM PIPE
+pushd "$tmpdir"
+
+URL=https://webkitgtk.org/jsc-built-products/x86_64/release
+LATEST=$(curl $URL/LAST-IS)
+VERSION=${LATEST%@main.zip}
+curl $URL/$LATEST --output main.zip
+filename="main.zip"
+unzip -q $filename -d jsc
+cipd create \
+  -name dart/third_party/jsc/linux-amd64 \
+  -in jsc \
+  -install-mode copy \
+  -tag version:$VERSION
+rm $filename
+rm -rf jsc
+popd
+
+gclient setdep --var="jsc_tag=version:$VERSION"