Add depfile support to android build scripts

build/android/gyp/javac.py

Index: build/android/gyp/javac.py
diff --git a/build/android/gyp/javac.py b/build/android/gyp/javac.py
index 694dd3aeb42721619fda0c367bce8b3b61a4bf56..599f5883ec9274d2745c336c8f5eb6c0eb4b8316 100755
--- a/build/android/gyp/javac.py
+++ b/build/android/gyp/javac.py
@@ -111,6 +111,8 @@ def main():
   colorama.init()
 
   parser = optparse.OptionParser()
+  build_utils.AddDepfileOption(parser)
+
   parser.add_option(
       '--src-gendirs',
       help='Directories containing generated java files.')
@@ -165,6 +167,11 @@ def main():
       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)