Add gyp flag to specify whether we should optimize JNI generation.

base/android/jni_generator/jni_generator.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Extracts native methods from a Java file and generates the JNI bindings.
 If you change this, please run and update the tests."""
 
 import collections
 import optparse
@@ skipping 939 matching lines @@
   out_dir = os.path.join(out_dir, os.path.dirname(input_file))
   if not os.path.exists(out_dir):
     os.makedirs(out_dir)
   extracted_file_name = os.path.join(out_dir, os.path.basename(input_file))
   with open(extracted_file_name, 'w') as outfile:
     outfile.write(jar_file.read(input_file))
 
   return extracted_file_name
 
 
-def GenerateJNIHeader(input_file, output_file, namespace):
+def GenerateJNIHeader(input_file, output_file, namespace, skip_if_same):
   try:
     if os.path.splitext(input_file)[1] == '.class':
       jni_from_javap = JNIFromJavaP.CreateFromClass(input_file, namespace)
       content = jni_from_javap.GetContent()
     else:
       jni_from_java_source = JNIFromJavaSource.CreateFromFile(input_file)
       content = jni_from_java_source.GetContent()
   except ParseError, e:
     print e
     sys.exit(1)
   if output_file:
     if not os.path.exists(os.path.dirname(os.path.abspath(output_file))):
       os.makedirs(os.path.dirname(os.path.abspath(output_file)))
+    if skip_if_same and os.path.exists(output_file):
+      with file(output_file, 'r') as f:
+        existing_content = f.read()
+        if existing_content == content:
+          return
     with file(output_file, 'w') as f:
       f.write(content)
   else:
     print output
 
 
 def main(argv):
   usage = """usage: %prog [OPTIONS]
 This script will parse the given java source code extracting the native
 declarations and print the header file to stdout (or a file).
 See SampleForTests.java for more details.
   """
   option_parser = optparse.OptionParser(usage=usage)
   option_parser.add_option('-j', dest='jar_file',
                            help='Extract the list of input files from'
                            ' a specified jar file.'
                            ' Uses javap to extract the methods from a'
                            ' pre-compiled class. --input should point'
                            ' to pre-compiled Java .class files.')
   option_parser.add_option('-n', dest='namespace',
                            help='Uses as a namespace in the generated header,'
                            ' instead of the javap class name.')
   option_parser.add_option('--input_file',
                            help='Single input file name. The output file name '
                            'will be derived from it. Must be used with '
                            '--output_dir.')
   option_parser.add_option('--output_dir',
                            help='The output directory. Must be used with '
                            '--input')
+  option_parser.add_option('--optimize_generation', type="int",
+                           default=0, help='Whether we should optimize JNI '
+                           'generation by not regenerating files if they have '
+                           'not changed.')
   options, args = option_parser.parse_args(argv)
   if options.jar_file:
     input_file = ExtractJarInputFile(options.jar_file, options.input_file,
                                      options.output_dir)
   else:
     input_file = options.input_file
   output_file = None
   if options.output_dir:
     root_name = os.path.splitext(os.path.basename(input_file))[0]
     output_file = os.path.join(options.output_dir, root_name) + '_jni.h'
-  GenerateJNIHeader(input_file, output_file, options.namespace)
+  GenerateJNIHeader(input_file, output_file, options.namespace,
+                    options.optimize_generation)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))