Android Add java_group() template to GN

build/config/android/rules.gni

 # 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.
 
 import("//base/android/linker/config.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/internal_rules.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 import("//third_party/android_platform/config.gni")
@@ skipping 728 matching lines @@
   }
 
   group(target_name) {
     forward_variables_from(invoker, [ "visibility" ])
     public_deps = [
       ":$_build_config_target_name",
     ]
   }
 }
 
+# Declare a group() that supports forwarding java dependency information.
+#
+# Example
+#  java_group("conditional_deps") {
+#    if (enable_foo) {
+#      deps = [":foo_java"]
+#    }
+#  }
+template("java_group") {
+  write_build_config("${target_name}__build_config") {
+    forward_variables_from(invoker, [ "deps" ])
+    type = "group"
+    build_config = "$target_gen_dir/${invoker.target_name}.build_config"
+  }
+  group(target_name) {
+    deps = []
+    forward_variables_from(invoker, "*")
+    deps += [ ":${target_name}__build_config" ]
+  }
+}
+
 # Declare a target that generates localized strings.xml from a .grd file.
 #
 # If this target is included in the deps of an android resources/library/apk,
 # the strings.xml will be included with that target.
 #
 # Variables
 #   deps: Specifies the dependencies of this target.
 #   grd_file: Path to the .grd file to generate strings.xml from.
 #   outputs: Expected grit outputs (see grit rule).
 #
@@ skipping 1561 matching lines @@
   }
 
   android_library(target_name) {
     java_files = []
     srcjar_deps = [ ":${_template_name}__protoc_java" ]
     deps = [
       "//third_party/android_protobuf:protobuf_nano_javalib",
     ]
   }
 }