Make javac invocations incremental when possible

build/android/gyp/jar.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 optparse
 import os
 import sys
 
@@ skipping 15 matching lines @@
   jar_cmd.extend(class_files_rel)
 
   with build_utils.TempDir() as temp_dir:
     empty_file = os.path.join(temp_dir, '.empty')
     build_utils.Touch(empty_file)
     jar_cmd.append(os.path.relpath(empty_file, jar_cwd))
     build_utils.CheckOutput(jar_cmd, cwd=jar_cwd)
     build_utils.Touch(jar_path, fail_if_missing=True)
 
 
-def JarDirectory(classes_dir, excluded_classes, jar_path, manifest_file=None):
+def JarDirectory(classes_dir, jar_path, manifest_file=None, predicate=None):
   class_files = build_utils.FindInDirectory(classes_dir, '*.class')
-  class_files = [f for f in class_files
-                 if not build_utils.MatchesGlob(f, excluded_classes)]
+  if predicate:
+    class_files = [f for f in class_files if predicate(f)]
 
   Jar(class_files, classes_dir, jar_path, manifest_file=manifest_file)
 
 
 def main():
   parser = optparse.OptionParser()
   parser.add_option('--classes-dir', help='Directory containing .class files.')
   parser.add_option('--jar-path', help='Jar output path.')
   parser.add_option('--excluded-classes',
       help='List of .class file patterns to exclude from the jar.')
   parser.add_option('--stamp', help='Path to touch on success.')
 
   options, _ = parser.parse_args()
 
+  predicate = None
   if options.excluded_classes:
     excluded_classes = build_utils.ParseGypList(options.excluded_classes)
-  else:
-    excluded_classes = []
-  JarDirectory(options.classes_dir,
-               excluded_classes,
-               options.jar_path)
+    predicate = lambda f: not build_utils.MatchesGlob(f, excluded_classes)
+
+  JarDirectory(options.classes_dir, options.jar_path, predicate=predicate)
 
   if options.stamp:
     build_utils.Touch(options.stamp)
 
 
 if __name__ == '__main__':
   sys.exit(main())