[RCS] Disable concurrent recompilation for callstats.py

We don't track concurrent recompilation/optimization in RCS, disabling it will
give us a better idea of the performance of our compilers.

Change-Id: I8138b09d5f112914f7c7929e9ece6f543423fd03
Reviewed-on: https://chromium-review.googlesource.com/436404Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#42901}

tools/callstats.py

@@ -177,7 +177,7 @@ def run_site(site, domain, args, timeout=None):
           user_data_dir = args.user_data_dir
         else:
           user_data_dir = tempfile.mkdtemp(prefix="chr_")
-        js_flags = "--runtime-call-stats"
+        js_flags = "--runtime-call-stats --noconcurrent-recompilation"
         if args.replay_wpr: js_flags += " --allow-natives-syntax"
         if args.js_flags: js_flags += " " + args.js_flags
         chrome_flags = get_chrome_flags(js_flags, user_data_dir)