Improve --help message for run_gpu_integration_test.

Tbr: nednguyen@google.com
No-Try: True
Bug: 898602
Change-Id: I7da27e4ddff3ff4f15f1b56c3067ff42ecb48a05
Reviewed-on: https://chromium-review.googlesource.com/c/1298197
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602454}

content/test/gpu/run_gpu_integration_test.py

@@ -61,6 +61,7 @@ def main():
   # we need the help output from both the argument parser here and the argument
   # parser in browser_test_runner.
   if '--help' in rest_args:
+    print '\n\nCommand line arguments handed by run_gpu_integration_test:'
     parser.print_help()
     return retval