android: Make javac rules depend on java files too.

build/java.gypi

 # 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.
 
 # This file is meant to be included into a target to provide a rule
 # to build Java in a consistent manner.
 #
 # To use this, create a gyp target with the following form:
 # {
 #   'target_name': 'my-package_java',
@@ skipping 262 matching lines @@
           ]
         },
       ],
     }],
   ],
   'actions': [
     {
       'action_name': 'javac_<(_target_name)',
       'message': 'Compiling <(_target_name) java sources',
       'variables': {
-        'java_source_list': '>|(javasources.<(_target_name).gypcmd >!@(find >(java_in_dir)/src >(additional_src_dirs) -name "*.java"))',
+        'java_sources': ['>!@(find >(java_in_dir)/src >(additional_src_dirs) -name "*.java")'],
+        'java_source_list': '>|(javasources.<(_target_name).gypcmd >@(java_sources))',
       },
       'inputs': [
         '<(DEPTH)/build/android/gyp/util/build_utils.py',
         '<(DEPTH)/build/android/gyp/javac.py',
+        '>@(java_sources)',
         '>(java_source_list)',
         '>@(input_jars_paths)',
         '>@(additional_input_paths)',
       ],
       'outputs': [
         '<(compile_stamp)',
       ],
       'action': [
         'python', '<(DEPTH)/build/android/gyp/javac.py',
         '--output-dir=<(classes_dir)',
@@ skipping 85 matching lines @@
             'dex_no_locals': 1,
           }],
         ],
         'dex_input_paths': [ '<(jar_final_path)' ],
         'output_path': '<(dex_path)',
       },
       'includes': [ 'android/dex_action.gypi' ],
     },
   ],
 }