[tools/perf] Fix file open mode in results processor

The text open mode caused proto trace corruption on Windows.

Change-Id: Idafef92472125a83352ffe8c4ee1484f45c1c561
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2390161
Auto-Submit: Mikhail Khokhlov <khokhlov@google.com>
Reviewed-by: Deep Roy <dproy@chromium.org>
Commit-Queue: Deep Roy <dproy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803868}

tools/perf/core/results_processor/processor.py

@@ -269,7 +269,7 @@ def AggregateTBMv3Traces(test_result):
     proto_files = [artifacts[name]['filePath'] for name in traces]
     concatenated_path = _BuildOutputPath(
         proto_files, compute_metrics.CONCATENATED_PROTO_NAME)
-    with open(concatenated_path, 'w') as concatenated_trace:
+    with open(concatenated_path, 'wb') as concatenated_trace:
       for trace_file in proto_files:
         if trace_file.endswith('.pb.gz'):
           with gzip.open(trace_file, 'rb') as f: