Build a Flutter.jar output for use by Android projects built without the Flutter tools

Flutter.jar contains the Flutter engine Java code, native code and resources.
It can be incorporated into projects built with external build systems such as Gradle.

build/android/gyp/create_flutter_jar.py

+#!/usr/bin/env python
+#
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Create a JAR incorporating all the components required to build a Flutter application"""
+
+import optparse
+import os
+import sys
+import zipfile
+
+from util import build_utils
+
+def main(args):
+  args = build_utils.ExpandFileArgs(args)
+  parser = optparse.OptionParser()
+  build_utils.AddDepfileOption(parser)
+  parser.add_option('--output', help='Path to output jar.')
+  parser.add_option('--dist_jar', help='Flutter shell Java code jar.')
+  parser.add_option('--native_lib', action='append', help='Native code library.')
+  parser.add_option('--android_abi', help='Native code ABI.')
+  parser.add_option('--asset_dir', help='Path to assets.')
+  options, _ = parser.parse_args(args)
+  build_utils.CheckOptions(options, parser, [
+    'output', 'dist_jar', 'native_lib', 'android_abi', 'asset_dir'
+  ])
+
+  input_deps = []
+
+  with zipfile.ZipFile(options.output, 'w') as out_zip:
+    input_deps.append(options.dist_jar)
+    with zipfile.ZipFile(options.dist_jar, 'r') as dist_zip:
+      for dist_file in dist_zip.infolist():
+        if dist_file.filename.endswith('.class'):
+          out_zip.writestr(dist_file.filename, dist_zip.read(dist_file.filename))
+
+    for native_lib in options.native_lib:
+      input_deps.append(native_lib)
+      out_zip.write(native_lib,
+                    'lib/%s/%s' % (options.android_abi, os.path.basename(native_lib)))
+
+    for asset_file in os.listdir(options.asset_dir):
+      input_deps.append(asset_file)
+      out_zip.write(os.path.join(options.asset_dir, asset_file),
+                    'assets/%s' % asset_file)
+
+  if options.depfile:
+    build_utils.WriteDepfile(
+        options.depfile,
+        input_deps + build_utils.GetPythonDependencies())
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))

build/config/android/rules.gni

@@ -1753,6 +1753,47 @@ template("android_apk") {
     }
   }
 
+  if (defined(invoker.flutter_dist_jar)) {
+    flutter_jar_target = "${_template_name}__create_flutter_jar"
+    final_deps += [ ":$flutter_jar_target" ]
+
+    action(flutter_jar_target) {
+      script = "//build/android/gyp/create_flutter_jar.py"
+      depfile = "$target_gen_dir/$target_name.d"
+      inputs = [
+        _dist_jar_path,
+      ]
+      outputs = [
+        invoker.flutter_dist_jar,
+      ]
+      args = [
+        "--depfile",
+        rebase_path(depfile, root_build_dir),
+        "--output",
+        rebase_path(invoker.flutter_dist_jar, root_build_dir),
+        "--dist_jar",
+        rebase_path(_dist_jar_path, root_build_dir),
+        "--android_abi",
+        "$android_app_abi",
+        "--asset_dir",
+        rebase_path(invoker.asset_location, root_build_dir),
+      ]
+      foreach(native_lib, rebase_path(_native_libs, root_build_dir)) {
+        args += [
+          "--native_lib",
+          native_lib,
+        ]
+      }
+      deps = [
+        ":$create_dist_target",
+        ":${_template_name}__prepare_native"
+      ]
+      if (defined(invoker.deps)) {
+        deps += invoker.deps
+      }
+    }
+  }
+
   group(target_name) {
     deps = final_deps
     if (defined(invoker.data_deps)) {

sky/shell/BUILD.gn

@@ -221,6 +221,8 @@ if (is_android) {
 
     extensions_to_not_compress = ".flx"
 
+    flutter_dist_jar = "$root_build_dir/flutter.jar"
+
     deps = [
       "//base:base_java",
       ":assets",