Add support for a custom test_runner.py script.

build/config/android/internal_rules.gni

Index: build/config/android/internal_rules.gni
diff --git a/build/config/android/internal_rules.gni b/build/config/android/internal_rules.gni
index ee151fbf81360c9175970e7b05ee159ffe40a1bc..5eaa1f6a39bb9fdabb5653cf3981a8801cde536e 100644
--- a/build/config/android/internal_rules.gni
+++ b/build/config/android/internal_rules.gni
@@ -591,6 +591,13 @@ template("test_runner_script") {
       "--script-output-path",
       rebase_path(generated_script, root_build_dir),
     ]
+    if (defined(test_runner_script)) {

[jbudorick, 2016/11/23 17:09:31]

I think this would have to be invoker.test_runner_script.

[ehmaldonado_chromium, 2016/11/23 17:19:32]

I was planning to have this be a variable in //build_overrides/build.gni. It
seems easier that way.
Maybe I should document it there as well?

[kjellander_chromium, 2016/11/23 20:05:40]

If we can avoid forcing downstream projects like V8 to add an entry to their
//build_overrides/build.gni I think it would be great. Things like that keeps
blocking their autoroller and is annoying. Wasn't there a way to do it without
needing that, or is that what John suggests?

+      args += [
+        "--test-runner-path",
+        test_runner_script,
+      ]
+    }
+
     args += test_runner_args
   }
 }