Add retrolambda.py and integrate it to build process.

build/android/gyp/retrolambda.py

Index: build/android/gyp/retrolambda.py
diff --git a/build/android/gyp/retrolambda.py b/build/android/gyp/retrolambda.py
new file mode 100755
index 0000000000000000000000000000000000000000..158ed52a1a4931e4637e3a669ae3e87525819f6d
--- /dev/null
+++ b/build/android/gyp/retrolambda.py
@@ -0,0 +1,68 @@
+#!/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.
+
+import argparse
+import os
+import shutil
+import sys
+import tempfile
+
+from util import build_utils
+
+
+_SRC_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                         '..', '..', '..'))
+_RETROLAMBDA_JAR_PATH = os.path.normpath(os.path.join(
+    _SRC_ROOT, 'third_party', 'retrolambda', 'retrolambda-2.3.0.jar'))
+
+
+def _OnStaleMd5(input_jar, output_jar, classpath, android_sdk_jar):
+  with build_utils.TempDir() as temp_dir:
+    build_utils.ExtractAll(input_jar, path=temp_dir)
+    cmd = [
+        'java',
+        '-Dretrolambda.inputDir=' + temp_dir,
+        '-Dretrolambda.classpath=' +
+            ':'.join([temp_dir] + classpath + [android_sdk_jar]),
+        '-javaagent:' + _RETROLAMBDA_JAR_PATH,
+        '-jar',
+        _RETROLAMBDA_JAR_PATH,
+    ]
+
+    build_utils.CheckOutput(cmd, print_stdout=False)
+    build_utils.ZipDir(output_jar + '.tmp', temp_dir)
+    shutil.move(output_jar + '.tmp', output_jar)
+
+
+def main():
+  args = build_utils.ExpandFileArgs(sys.argv[1:])
+  parser = argparse.ArgumentParser()
+  build_utils.AddDepfileOption(parser)
+  parser.add_argument('--input-jar', required=True,
+                      help='Jar input path to include .class files from.')
+  parser.add_argument('--output-jar', required=True,
+                      help='Jar output path.')
+  parser.add_argument('--classpath', required=True,
+                      help='Classpath.')
+  parser.add_argument('--android-sdk-jar', required=True,
+                      help='Android sdk jar path.')
+  options = parser.parse_args(args)
+
+  options.classpath = build_utils.ParseGnList(options.classpath)
+  input_paths = options.classpath + [options.input_jar]
+  output_paths = [options.output_jar]
+
+  build_utils.CallAndWriteDepfileIfStale(
+      lambda: _OnStaleMd5(options.input_jar, options.output_jar,
+                          options.classpath, options.android_sdk_jar),
+      options,
+      input_paths=input_paths,
+      input_strings=[],
+      output_paths=output_paths)
+
+
+if __name__ == '__main__':
+  sys.exit(main())