Add CIPD dependency for Dart DevTools

Pulls a pre-built DevTools into the SDK and provides an update script to
pull DevTools, rebuild at a particular revision, and upload the new
build to CIPD.

Change-Id: Ice7a9b6bfeea333bc2769dadaeba6eb11fc033d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/187161
Reviewed-by: Siva Annamalai <asiva@google.com>

DEPS

@@ -229,6 +229,13 @@ deps = {
       }],
       "dep_type": "cipd",
   },
+  Var("dart_root") + "/third_party/devtools": {
+      "packages": [{
+          "package": "dart/third_party/flutter/devtools",
+          "version": "revision:6729ec62c3548839018c32fa711756202431ccf7",
+      }],
+      "dep_type": "cipd",
+  },
   Var("dart_root") + "/tests/co19/src": {
       "packages": [{
           "package": "dart/third_party/co19",

third_party/devtools/README

@@ -0,0 +1,14 @@
+This folder contains a pre-built Dart DevTools instance which can be served
+as a web application, as well as the package:devtools_server and package:devtools_shared
+from the same revision, used to host and launch DevTools from a Dart process.
+
+First, ensure Flutter is installed and on your path (see https://flutter.dev/docs/get-started/install/linux#install-flutter-manually).
+
+With `flutter` on your path, do the following:
+
+- Run ./update.sh <revision> to build DevTools at a given revision and upload it
+  to CIPD. The uploaded CIPD entry will be tagged with `revision:<revision>`
+- Update DEPS to point to the newly updated DevTools by providing "revision:<revision>"
+  as the version entry for "third_party/devtools"
+
+DevTools CIPD packages are located at https://chrome-infra-packages.appspot.com/p/dart/third_party/flutter/devtools/+/.

third_party/devtools/update.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+
+# Copyright 2021 The Dart Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -ex #echo on
+
+if [ -z "$1" ]; then
+  echo "Usage: update.sh revision"
+  exit 1
+fi
+
+tmpdir=$(mktemp -d)
+cleanup() {
+  rm -rf "$tmpdir"
+}
+
+trap cleanup EXIT HUP INT QUIT TERM PIPE
+cd "$tmpdir"
+
+# Clone DevTools and build.
+git clone git@github.com:flutter/devtools.git
+cd devtools
+git checkout -b cipd_release $1
+
+./tool/build_release.sh
+
+# Copy the build output as well as the devtools packages needed
+# to serve from DDS.
+mkdir cipd_package
+cp -R packages/devtools/build/ cipd_package/web
+cp -r packages/devtools_server cipd_package
+cp -r packages/devtools_shared cipd_package
+
+cipd create \
+  -name dart/third_party/flutter/devtools \
+  -in cipd_package \
+  -install-mode copy \
+  -tag revision:$1
+