trace_processor: refactor diff testing framework to prep for perf tests

Change-Id: If5c1b06d5221095bbd41ea3e53b6adc08625f34c
Bug: 131354532
diff --git a/src/trace_processor/trace_processor_shell.cc b/src/trace_processor/trace_processor_shell.cc
index 31464a3..b8b690d 100644
--- a/src/trace_processor/trace_processor_shell.cc
+++ b/src/trace_processor/trace_processor_shell.cc
@@ -589,7 +589,7 @@
     return 1;
   }
 
-  auto fd(base::OpenFile(perf_file_path, O_WRONLY | O_CREAT | O_TRUNC, 066));
+  auto fd(base::OpenFile(perf_file_path, O_WRONLY | O_CREAT | O_TRUNC, 0666));
   if (!fd) {
     PERFETTO_ELOG("Failed to open perf file");
     return 1;