Add helper gypi for predexing of prebuilt jars.

build/java_prebuilt.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 package prebuilt Java JARs in a consistent manner.
+#
+# To use this, create a gyp target with the following form:
+# {
+#   'target_name': 'my-package_java',
+#   'type': 'none',
+#   'variables': {
+#     'jar_path': 'path/to/your.jar',
+#   },
+#   'includes': ['path/to/this/gypi/file'],
+# }
+#
+# Required variables:
+#  jar_path - The path to the prebuilt Java JAR file.
+
+{
+  'dependencies': [
+    '<(DEPTH)/build/build_output_dirs_android.gyp:build_output_dirs'
+  ],
+  'variables': {
+    'dex_path': '<(PRODUCT_DIR)/lib.java/<(_target_name).dex.jar',
+  },
+  'all_dependent_settings': {
+    'variables': {
+      'input_jars_paths': ['<(jar_path)'],
+      'library_dexed_jars_paths': ['<(dex_path)'],
+    },
+  },
+  'actions': [
+    {
+      'action_name': 'dex_<(_target_name)',
+      'message': 'Dexing <(_target_name) jar',
+      'inputs': [
+        '<(DEPTH)/build/android/pylib/build_utils.py',
+        '<(DEPTH)/build/android/dex.py',
+        '<(jar_path)',
+      ],
+      'outputs': [
+        '<(dex_path)',
+      ],
+      'action': [
+        'python', '<(DEPTH)/build/android/dex.py',
+        '--dex-path=<(dex_path)',
+        '--android-sdk-root=<(android_sdk_root)',
+
+        # TODO(newt): remove this once http://crbug.com/177552 is fixed in ninja.
+        '--ignore=>!(echo \'>(_inputs)\' | md5sum)',
+
+        '<(jar_path)',
+      ]
+    },
+
+  ],
+}