Add support for generating jars from protos and add cacheinvalidation_java.

build/protoc.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 invoke protoc in a consistent manner.
+# to invoke protoc in a consistent manner. For Java-targets, see
+# protoc_java.gypi.
 #
 # To use this, create a gyp target with the following form:
 # {
 #   'target_name': 'my_proto_lib',
 #   'type': 'static_library',
 #   'sources': [
 #     'foo.proto',
 #     'bar.proto',
 #   ],
 #   'variables': {
@@ skipping 90 matching lines @@
   },
   'export_dependent_settings': [
     # The generated headers reference headers within protobuf_lite,
     # so dependencies must be able to find those headers too.
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
   ],
   # This target exports a hard dependency because it generates header
   # files.
   'hard_dependency': 1,
 }