Add support for a custom test_runner.py script.

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.
 
 # Do not add any imports to non-//build directories here.
 # Some projects (e.g. V8) do not have non-build directories DEPS'ed in.
 import("//build_overrides/build.gni")
 import("//build/config/android/config.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/sanitizers/sanitizers.gni")
@@ skipping 573 matching lines @@
       generated_script,
     ]
     data += [ generated_script ]
 
     args = [
       "--depfile",
       rebase_path(depfile, root_build_dir),
       "--script-output-path",
       rebase_path(generated_script, root_build_dir),
     ]
+    if (defined(android_test_runner_script)) {
+      args += [
+        "--test-runner-path",
+        android_test_runner_script,
+      ]
+    }
+
     args += test_runner_args
   }
 }
 
 if (enable_java_templates) {
   import("//build/config/zip.gni")
   import("//third_party/ijar/ijar.gni")
   import("//third_party/android_platform/config.gni")
 
   rebased_android_sdk = rebase_path(android_sdk, root_build_dir)
@@ skipping 2119 matching lines @@
         rebase_path(root_build_dir, root_build_dir),
         "--packed-libraries-dir",
         rebase_path(_packed_libraries_dir, root_build_dir),
         "--libraries=${invoker.libraries_filearg}",
         "--filelistjson",
         rebase_path(invoker.file_list_json, root_build_dir),
       ]
     }
   }
 }