Add token to stderr as well as stdout for batch processing.

tools/testing/run_selenium.py

Index: tools/testing/run_selenium.py
diff --git a/tools/testing/run_selenium.py b/tools/testing/run_selenium.py
index 8f129fb759ae4be580a392e317634ccd7bf6acfa..0e8f0a6bd1ee5d426ca35bab4f984d99b26139ed 100755
--- a/tools/testing/run_selenium.py
+++ b/tools/testing/run_selenium.py
@@ -242,6 +242,10 @@ def run_batch_tests():
 
       source = run_test_in_browser(browser, html_out, timeout, is_perf)
 
+      # Test is done. Write end token to stderr and flush.
+      sys.stderr.write('>>> EOF STDERR\n')
+      sys.stderr.flush()
+
       # print one of:
       # >>> TEST {PASS, FAIL, OK, CRASH, FAIL, TIMEOUT}
       status = report_results(is_perf, source)