GN + Android: support standalone .dex.jar output of Android libraries.

build/config/android/internal_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("//build/config/android/config.gni")
 
 assert(is_android)
 
 rebased_android_sdk = rebase_path(android_sdk, root_build_dir)
 rebased_android_sdk_root = rebase_path(android_sdk_root, root_build_dir)
@@ skipping 878 matching lines @@
       }
     }
 
     _final_deps += [ ":${_template_name}__dex" ]
     dex("${_template_name}__dex") {
       sources = [
         _jar_path,
       ]
       output = _dex_path
     }
+
+    if (defined(invoker.standalone_dex_path)) {
+      _final_deps += [ ":${_template_name}__standalone_dex" ]
+      _rebased_build_config = rebase_path(_build_config, root_build_dir)
+      dex("${_template_name}__standalone_dex") {
+        sources = [_jar_path]
+        inputs = [_build_config]
+        output = invoker.standalone_dex_path
+        dex_arg_key = "${_rebased_build_config}:final_dex:dependency_dex_files"
+        args = [ "--inputs=@FileArg($dex_arg_key)" ]
+      }
+    }
   }
 
   group(target_name) {
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     deps = _final_deps
     datadeps = _final_datadeps
   }
 }
@@ skipping 125 matching lines @@
 
     if (defined(invoker.clear_dir) && invoker.clear_dir) {
       args += [ "--clear" ]
     }
 
     if (defined(invoker.args)) {
       args += invoker.args
     }
   }
 }