diff --git a/DEPS b/DEPS
index 9fd48200f1..580518a5c6 100644
--- a/DEPS
+++ b/DEPS
@@ -135,7 +135,7 @@ deps = {
 
   'src/third_party/khronos':
    Var('chromium_git') + '/chromium/src/third_party/khronos.git' + '@' + '7122230e90547962e0f0c627f62eeed3c701f275',
-  
+
   'src/third_party/googletest':
    Var('github_git') + '/google/googletest' + '@' + 'f5e592d8ee5ffb1d9af5be7f715ce3576b8bf9c4',
 
@@ -598,12 +598,6 @@ hooks = [
     'pattern': '.',
     'action': ['python', 'src/build/vs_toolchain.py', 'update'],
   },
-  {
-    'name': 'generate_package_files',
-    'pattern': '.',
-    'cwd': 'src/',
-    'action': ['python', 'flutter/tools/generate_package_files.py'],
-  },
   {
     # Ensure that we don't accidentally reference any .pyc files whose
     # corresponding .py files have already been deleted.
@@ -659,11 +653,11 @@ hooks = [
       '--arch=arm64'],
   },
   {
-    'name': 'dart package config',
+    'name': 'pub get --offline',
     'pattern': '.',
     'action': [
       'python',
-      'src/flutter/tools/run_third_party_dart.py',
+      'src/flutter/tools/pub_get_offline.py',
     ]
   },
   {
diff --git a/engine/src/flutter/flutter_frontend_server/pubspec.yaml b/engine/src/flutter/flutter_frontend_server/pubspec.yaml
index 8cb5021d80..330b3c6e3d 100644
--- a/engine/src/flutter/flutter_frontend_server/pubspec.yaml
+++ b/engine/src/flutter/flutter_frontend_server/pubspec.yaml
@@ -1,9 +1,18 @@
-name: frontend_server
+name: flutter_frontend_server
+publish_to: none
 version: 0.1.1-dev
 description: Communication pipe to Dart Frontend
-homepage: http://flutter.io
+homepage: https://flutter.dev
 author: Flutter Authors <flutter-dev@googlegroups.com>
 
+# Do not add any dependencies that require more than what is provided in
+# //third_party/dart/pkg or //third_party/dart/third_party/pkg.
+# In particular, package:test is not usable here.
+
+# If you do add packages here, make sure you can run `pub get --offline`, and
+# check the .packages and .package_config to make sure all the paths are
+# relative to this directory into //third_party/dart
+
 environment:
   sdk: ">=2.2.2 <3.0.0"
 
@@ -15,13 +24,75 @@ dependencies:
   convert: any
   crypto: any
   front_end: any
+  frontend_server: any
   kernel: any
   logging: any
   meta: any
-  quiver: any
   package_config: any
   path: any
   source_span: any
   typed_data: any
   usage: any
   vm: any
+
+dependency_overrides:
+  _fe_analyzer_shared:
+    path: ../../third_party/dart/pkg/_fe_analyzer_shared
+  _js_interop_checks:
+    path: ../../third_party/dart/pkg/_js_interop_checks
+  args:
+    path: ../../third_party/dart/third_party/pkg/args
+  async:
+    path: ../../third_party/dart/third_party/pkg/async
+  bazel_worker:
+    path: ../../third_party/dart/third_party/pkg/bazel_worker
+  build_integration:
+    path: ../../third_party/dart/pkg/build_integration
+  charcode:
+    path: ../../third_party/dart/third_party/pkg/charcode
+  cli_util:
+    path: ../../third_party/dart/third_party/pkg/cli_util
+  collection:
+    path: ../../third_party/dart/third_party/pkg/collection
+  convert:
+    path: ../../third_party/dart/third_party/pkg/convert
+  crypto:
+    path: ../../third_party/dart/third_party/pkg/crypto
+  dev_compiler:
+    path: ../../third_party/dart/pkg/dev_compiler
+  fixnum:
+    path: ../../third_party/dart/third_party/pkg/fixnum
+  front_end:
+    path: ../../third_party/dart/pkg/front_end
+  frontend_server:
+    path: ../../third_party/dart/pkg/frontend_server
+  kernel:
+    path: ../../third_party/dart/pkg/kernel
+  logging:
+    path: ../../third_party/dart/third_party/pkg/logging
+  matcher:
+    path: ../../third_party/dart/third_party/pkg/matcher
+  meta:
+    path: ../../third_party/dart/pkg/meta
+  package_config:
+    path: ../../third_party/dart/third_party/pkg_tested/package_config
+  path:
+    path: ../../third_party/dart/third_party/pkg/path
+  pedantic:
+    path: ../../third_party/dart/third_party/pkg/pedantic
+  protobuf:
+    path: ../../third_party/dart/third_party/pkg/protobuf/protobuf
+  source_maps:
+    path: ../../third_party/dart/third_party/pkg/source_maps
+  source_span:
+    path: ../../third_party/dart/third_party/pkg/source_span
+  stack_trace:
+    path: ../../third_party/dart/third_party/pkg/stack_trace
+  term_glyph:
+    path: ../../third_party/dart/third_party/pkg/term_glyph
+  typed_data:
+    path: ../../third_party/dart/third_party/pkg/typed_data
+  usage:
+    path: ../../third_party/dart/third_party/pkg/usage
+  vm:
+    path: ../../third_party/dart/pkg/vm
diff --git a/engine/src/flutter/tools/const_finder/.dart_tool/package_config.json b/engine/src/flutter/tools/const_finder/.dart_tool/package_config.json
deleted file mode 100644
index ab6318f181..0000000000
--- a/engine/src/flutter/tools/const_finder/.dart_tool/package_config.json
+++ /dev/null
@@ -1,41 +0,0 @@
-{
-  "configVersion": 2,
-  "packages": [
-    {
-      "name": "const_finder",
-      "rootUri": "../",
-      "packageUri": "lib",
-      "languageVersion": "2.4"
-    },
-    {
-      "name": "kernel",
-      "rootUri": "../../../../third_party/dart/pkg/kernel",
-      "packageUri": "lib",
-      "languageVersion": "2.12"
-    },
-    {
-      "name": "meta",
-      "rootUri": "../../../../third_party/dart/pkg/meta",
-      "packageUri": "lib",
-      "languageVersion": "2.12"
-    },
-    {
-      "name": "args",
-      "rootUri": "../../../../third_party/dart/third_party/pkg/args",
-      "packageUri": "lib",
-      "languageVersion": "2.12"
-    },
-    {
-      "name": "collection",
-      "rootUri": "../../../../third_party/dart/third_party/pkg/collection",
-      "packageUri": "lib",
-      "languageVersion": "2.12"
-    },
-    {
-      "name": "path",
-      "rootUri": "../../../../third_party/dart/third_party/pkg/path",
-      "packageUri": "lib",
-      "languageVersion": "2.12"
-    }
-  ]
-}
\ No newline at end of file
diff --git a/engine/src/flutter/tools/const_finder/.gitignore b/engine/src/flutter/tools/const_finder/.gitignore
index da3df735e8..fb0d5a5d34 100644
--- a/engine/src/flutter/tools/const_finder/.gitignore
+++ b/engine/src/flutter/tools/const_finder/.gitignore
@@ -1,6 +1,5 @@
 *.dill
 
-!.dart_tool
-!.dart_tool/package_config.json
-!.packages
+!test/fixtures/.dart_tool
+!test/fixtures/.dart_tool/package_config.json
 !test/fixtures/.packages
diff --git a/engine/src/flutter/tools/const_finder/.packages b/engine/src/flutter/tools/const_finder/.packages
deleted file mode 100644
index 3ce2ffee72..0000000000
--- a/engine/src/flutter/tools/const_finder/.packages
+++ /dev/null
@@ -1,7 +0,0 @@
-# Generated by pub on 2020-11-27 10:12:47.813477.
-args:../../../third_party/dart/third_party/pkg/args/lib/
-collection:../../../third_party/dart/third_party/pkg/collection/lib/
-kernel:../../../third_party/dart/pkg/kernel/lib/
-meta:../../../third_party/dart/pkg/meta/lib/
-path:../../../third_party/dart/third_party/pkg/path/lib/
-const_finder:lib/
diff --git a/engine/src/flutter/tools/generate_package_config/bin/generate_from_legacy.dart b/engine/src/flutter/tools/generate_package_config/bin/generate_from_legacy.dart
deleted file mode 100644
index f7aa918712..0000000000
--- a/engine/src/flutter/tools/generate_package_config/bin/generate_from_legacy.dart
+++ /dev/null
@@ -1,97 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// @dart=2.8
-import 'dart:convert';
-import 'dart:io';
-
-import 'package:package_config/package_config.dart';
-import 'package:package_config/packages_file.dart';
-import 'package:package_config/src/package_config_json.dart';
-import 'package:pub_semver/pub_semver.dart';
-import 'package:yaml/yaml.dart';
-
-void main(List<String> args) async {
-  if (args.length != 1) {
-    throw ArgumentError('Unexpected arguments $args\n\n$usage');
-  }
-  if (args.first == 'help') {
-    print(usage);
-    return;
-  }
-  var packagesUri = Uri.base.resolve(args.first);
-  var packagesFile = File.fromUri(packagesUri);
-  if (!await packagesFile.exists()) {
-    throw ArgumentError('Unable to read file at `$packagesUri`');
-  }
-  var packageMap = parse(await packagesFile.readAsBytes(), packagesFile.uri);
-  var packages = <Package>[];
-  for (var packageEntry in packageMap.entries) {
-    var name = packageEntry.key;
-    var uri = packageEntry.value;
-    if (uri.scheme != 'file') {
-      throw ArgumentError(
-          'Only file: schemes are supported, but the `$name` package has '
-          'the following uri: ${uri}');
-    }
-    Uri packageRoot;
-    Uri pubspec;
-    LanguageVersion languageVersion;
-    // Pub packages will always have a path ending in `lib/`, and a pubspec
-    // directly above that.
-    if (uri.path.endsWith('lib/')) {
-      packageRoot = uri.resolve('../');
-      pubspec = packageRoot.resolve('pubspec.yaml');
-      if (!File.fromUri(pubspec).existsSync()) {
-        continue;
-      }
-      // Default to 2.7 if not found to prevent all packages from accidentally
-      // opting into NNBD.
-      languageVersion = await languageVersionFromPubspec(pubspec, name) ??
-          LanguageVersion(2, 7);
-      packages.add(Package(name, packageRoot,
-          languageVersion: languageVersion, packageUriRoot: uri));
-    }
-  }
-  var outputFile =
-      File.fromUri(packagesFile.uri.resolve('.dart_tool/package_config.json'));
-  if (!outputFile.parent.existsSync()) {
-    outputFile.parent.createSync();
-  }
-  var baseUri = outputFile.uri;
-  var sink = outputFile.openWrite(encoding: utf8);
-  writePackageConfigJsonUtf8(PackageConfig(packages), baseUri, sink);
-  await sink.close();
-}
-
-const usage = 'Usage: pub run package_config:generate_from_legacy <input-file>';
-
-Future<LanguageVersion> languageVersionFromPubspec(
-    Uri pubspec, String packageName) async {
-  var pubspecFile = File.fromUri(pubspec);
-  if (!await pubspecFile.exists()) {
-    return null;
-  }
-  var pubspecYaml =
-      loadYaml(await pubspecFile.readAsString(), sourceUrl: pubspec) as YamlMap;
-
-  // Find the sdk constraint, or return null if none is present
-  var environment = pubspecYaml['environment'] as YamlMap;
-  if (environment == null) {
-    return null;
-  }
-  var sdkConstraint = environment['sdk'] as String;
-  if (sdkConstraint == null) {
-    return null;
-  }
-
-  var parsedConstraint = VersionConstraint.parse(sdkConstraint);
-  var min = parsedConstraint is Version
-      ? parsedConstraint
-      : parsedConstraint is VersionRange
-          ? parsedConstraint.min
-          : throw 'Unsupported version constraint type $parsedConstraint';
-
-  return LanguageVersion(min.major, min.minor);
-}
diff --git a/engine/src/flutter/tools/generate_package_config/pubspec.yaml b/engine/src/flutter/tools/generate_package_config/pubspec.yaml
deleted file mode 100644
index 1afb2e21c5..0000000000
--- a/engine/src/flutter/tools/generate_package_config/pubspec.yaml
+++ /dev/null
@@ -1,8 +0,0 @@
-name: generate_package_config
-environment:
-  sdk: ">=2.8.0 <3.0.0"
-
-dependencies:
-  yaml: any
-  pub_semver: any
-  package_config: 1.9.3
diff --git a/engine/src/flutter/tools/generate_package_files.py b/engine/src/flutter/tools/generate_package_files.py
deleted file mode 100644
index 1eb1e6f6c0..0000000000
--- a/engine/src/flutter/tools/generate_package_files.py
+++ /dev/null
@@ -1,36 +0,0 @@
-#!/usr/bin/env python
-# Copyright 2013 The Flutter Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-# This script generates .packages file for frontend_server from Dart SDKs
-# .packages file located in  third_party/dart/.packages
-
-import os
-import shutil
-
-ALL_PACKAGES = {
-  'flutter_frontend_server': [],
-}
-
-SRC_DIR = os.getcwd()
-
-DOT_PACKAGES = '.packages'
-DART_PACKAGES_FILE = os.path.join(SRC_DIR, 'third_party', 'dart', DOT_PACKAGES)
-
-# Generate .packages file in the given package.
-def GeneratePackages(package, local_deps):
-  with open(os.path.join('flutter', package, DOT_PACKAGES), 'w') as packages:
-    with open(DART_PACKAGES_FILE, 'r') as dart_packages:
-      for line in dart_packages:
-        if line.startswith('#'):
-          packages.write(line)
-        else:
-          [name, path] = line.split(':', 1)
-          packages.write('%s:../../third_party/dart/%s' % (name, path))
-    packages.write('%s:./lib\n' % (package))
-    for other_package in local_deps:
-      packages.write('%s:../%s/lib\n' % (other_package, other_package))
-
-for package, local_deps in ALL_PACKAGES.iteritems():
-  GeneratePackages(package, local_deps)
diff --git a/engine/src/flutter/tools/pub_get_offline.py b/engine/src/flutter/tools/pub_get_offline.py
new file mode 100644
index 0000000000..a0ef4b23f7
--- /dev/null
+++ b/engine/src/flutter/tools/pub_get_offline.py
@@ -0,0 +1,72 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This python script uses `pub get --offline` to fill in
+# .dart_tool/package_config.json files for Dart packages in the tree whose
+# dependencies should be entirely resolved without requesting data from pub.dev.
+# This allows us to be certain that the Dart code we are pulling for these
+# packages is explicitly fetched by `gclient sync` rather than implicitly
+# fetched by pub version solving, and pub fetching transitive dependencies.
+
+import json
+import os
+import subprocess
+import sys
+
+ALL_PACKAGES = [
+  os.path.join("src", "flutter", "flutter_frontend_server"),
+  os.path.join("src", "flutter", "tools", "const_finder"),
+]
+
+
+def FetchPackage(pub, package):
+  try:
+    subprocess.check_output(pub, cwd=package, stderr=subprocess.STDOUT)
+  except subprocess.CalledProcessError as err:
+    print("'%s' failed in '%s' with status %d:\n%s" %
+          (' '.join(cmd), cwd, err.returncode, err.output))
+    return 1
+  return 0
+
+
+def CheckPackage(package):
+  package_config = os.path.join(package, ".dart_tool", "package_config.json")
+  pub_count = 0
+  with open(package_config) as f:
+    data_dict = json.load(f)
+    packages_data = data_dict["packages"]
+    for package_data in packages_data:
+      package_uri = package_data["rootUri"]
+      package_name = package_data["name"]
+      if ".pub-cache" in package_uri and "pub.dartlang.org" in package_uri:
+        print("Error: package '%s' was fetched from pub" % package_name)
+        pub_count = pub_count + 1
+  if pub_count > 0:
+    print("Error: %d packages were fetched from pub for %s" % (pub_count, package))
+    print("Please fix the pubspec.yaml for %s "
+          "so that all dependencies are path dependencies" % package)
+  return pub_count
+
+
+def Main():
+  leading = os.path.join("src", "third_party", "dart", "tools", "sdks", "dart-sdk", "bin")
+  pub = "pub"
+  if os.name == "nt":
+    pub = "pub.bat"
+  pubcmd = [os.path.abspath(os.path.join(leading, pub)), "get", "--offline"]
+
+  pub_count = 0
+  for package in ALL_PACKAGES:
+    if FetchPackage(pubcmd, package) != 0:
+      return 1
+    pub_count = pub_count + CheckPackage(package)
+
+  if pub_count > 0:
+    return 1
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(Main())
diff --git a/engine/src/flutter/tools/run_third_party_dart.py b/engine/src/flutter/tools/run_third_party_dart.py
deleted file mode 100644
index 9fef936ec0..0000000000
--- a/engine/src/flutter/tools/run_third_party_dart.py
+++ /dev/null
@@ -1,15 +0,0 @@
-# Copyright 2013 The Flutter Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import subprocess
-import os
-
-if __name__ == '__main__':
-    leading = os.path.join("src", "third_party", "dart", "tools", "sdks", "dart-sdk", "bin")
-    pub = "pub"
-    if os.name == "nt":
-        pub = "pub.bat"
-    subprocess.check_call([os.path.join(leading, pub), "global", "activate", "-spath", "./src/flutter/tools/generate_package_config"])
-    subprocess.check_call([os.path.join(leading, pub), "global", "run", "generate_package_config:generate_from_legacy", "src/flutter/flutter_frontend_server/.packages"])
-    subprocess.check_call([os.path.join(leading, pub), "global", "run", "generate_package_config:generate_from_legacy", "src/flutter/tools/const_finder/.packages"])