Fix java_cpp_enum.gypi so that source_file changes will rebuild dependencies.

build/android/java_cpp_enum.gypi

 # Copyright 2014 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.
 
 # This file is meant to be included into a target to provide an action
 # to generate Java source files from a C++ header file containing annotated
 # enum definitions using a Python script.
 #
 # To use this, create a gyp target with the following form:
 #  {
@@ skipping 15 matching lines @@
     'generator_path': '<(DEPTH)/build/android/gyp/java_cpp_enum.py',
     'generator_args': '<(output_dir) <(source_file)',
   },
   'direct_dependent_settings': {
     'variables': {
       # Ensure that the output directory is used in the class path
       # when building targets that depend on this one.
       'generated_src_dirs': [
         '<(output_dir)/',
       ],
+      # Ensure that the targets depending on this one are rebuilt if the sources
+      # of this one are modified.
+      'additional_input_paths': [
+        '<(source_file)',
+      ],
     },
   },
   'actions': [
     {
       'action_name': 'generate_java_constants',
       'inputs': [
         '<(DEPTH)/build/android/gyp/util/build_utils.py',
         '<(generator_path)',
         '<(source_file)',
       ],
       'outputs': [
         # This is the main reason this is an action and not a rule. Gyp doesn't
         # properly expand RULE_INPUT_PATH here and so it's impossible to
         # calculate the list of outputs.
         '<!@pymod_do_main(java_cpp_enum --print_output_only '
             '<@(generator_args))',
       ],
       'action': [
         'python', '<(generator_path)', '<@(generator_args)'
       ],
       'message': 'Generating Java from cpp header <(source_file)',
     },
   ],
 }