Add retrolambda.py and integrate it to build process.

build/android/gyp/javac.py

 #!/usr/bin/env python
 #
 # Copyright 2013 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 distutils.spawn
 import optparse
 import os
 import shutil
 import re
 import sys
 import textwrap
 
 from util import build_utils
 from util import md5_check
 
@@ skipping 295 matching lines @@
   parser.add_option('--jar-path', help='Jar output path.')
   parser.add_option('--stamp', help='Path to touch on success.')
 
   options, args = parser.parse_args(argv)
   build_utils.CheckOptions(options, parser, required=('jar_path',))
 
   bootclasspath = []
   for arg in options.bootclasspath:
     bootclasspath += build_utils.ParseGnList(arg)
   options.bootclasspath = bootclasspath
+  if options.java_version == '1.8' and options.bootclasspath:
+    # Android's boot jar doesn't contain all java 8 classes.
+    # See: https://github.com/evant/gradle-retrolambda/issues/23.
+    javac_path = os.path.realpath(distutils.spawn.find_executable('javac'))
+    jdk_dir = os.path.dirname(os.path.dirname(javac_path))
+    rt_jar = os.path.join(jdk_dir, 'jre', 'lib', 'rt.jar')
+    options.bootclasspath.append(rt_jar)
 
   classpath = []
   for arg in options.classpath:
     classpath += build_utils.ParseGnList(arg)
   options.classpath = classpath
 
   java_srcjars = []
   for arg in options.java_srcjars:
     java_srcjars += build_utils.ParseGnList(arg)
   options.java_srcjars = java_srcjars
@@ skipping 107 matching lines @@
       options,
       input_paths=input_paths,
       input_strings=javac_cmd,
       output_paths=output_paths,
       force=force,
       pass_changes=True)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))