Add depfile support to android build scripts

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 fnmatch
 import optparse
 import os
 import shutil
@@ skipping 93 matching lines @@
       Compile,
       record_path=record_path,
       input_paths=java_files + jar_inputs,
       input_strings=javac_cmd)
 
 
 def main():
   colorama.init()
 
   parser = optparse.OptionParser()
+  build_utils.AddDepfileOption(parser)
+
   parser.add_option(
       '--src-gendirs',
       help='Directories containing generated java files.')
   parser.add_option('--classpath', help='Classpath for javac.')
   parser.add_option(
       '--javac-includes',
       help='A list of file patterns. If provided, only java files that match' +
       'one of the patterns will be compiled.')
   parser.add_option(
       '--jar-excluded-classes',
@@ skipping 34 matching lines @@
 
     if options.classes_dir:
       # Delete the old classes directory. This ensures that all .class files in
       # the output are actually from the input .java files. For example, if a
       # .java file is deleted or an inner class is removed, the classes
       # directory should not contain the corresponding old .class file after
       # running this action.
       build_utils.DeleteDirectory(options.classes_dir)
       shutil.copytree(classes_dir, options.classes_dir)
 
+  if options.depfile:
+    build_utils.WriteDepfile(
+        options.depfile,
+        build_utils.GetPythonDependencies())
+
   if options.stamp:
     build_utils.Touch(options.stamp)
 
 
 if __name__ == '__main__':
   sys.exit(main())