Add ignore_true to rmtree in run_telemetry_benchmark_as_googletest

NOTRY=true  # webkit_layout_test flake

Bug: 865896
Change-Id: I388b256c6d39c0d3978bc17dad20cc5450ef3628
Reviewed-on: https://chromium-review.googlesource.com/1144726
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576858}

testing/scripts/run_telemetry_benchmark_as_googletest.py

@@ -167,7 +167,10 @@ def run_benchmark(args, rest_args, histogram_results):
           results, indent=2)
     valid = False
   finally:
-    shutil.rmtree(tempfile_dir)
+    # Add ignore_errors=True because otherwise rmtree may fail due to leaky
+    # processes of tests are still holding opened handles to files under
+    # |tempfile_dir|. For example, see crbug.com/865896
+    shutil.rmtree(tempfile_dir, ignore_errors=True)
 
   if not valid and num_failures == 0:
     if rc == 0: