[tools] Allow to increase number of times a perf test is retried

R=machenbach@chromium.org

No-Try: true
Bug: chromium:775123
Change-Id: I8883be60cc4860fad572ba644bbc722972551eb3
Reviewed-on: https://chromium-review.googlesource.com/1168483Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54999}

tools/run_perf.py

@@ -938,6 +938,9 @@ def Main(args):
                     "--filter=JSTests/TypedArrays/ will run only TypedArray "
                     "benchmarks from the JSTests suite.",
                     default="")
+  parser.add_option("--run-count-multiplier", default=1, type="int",
+                    help="Multipled used to increase number of times each test "
+                    "is retried.")
 
   (options, args) = parser.parse_args(args)
 
@@ -1042,7 +1045,8 @@ def Main(args):
 
         def Runner():
           """Output generator that reruns several times."""
-          for i in xrange(0, max(1, runnable.run_count)):
+          total_runs = runnable.run_count * options.run_count_multiplier
+          for i in xrange(0, max(1, total_runs)):
             # TODO(machenbach): Allow timeout per arch like with run_count per
             # arch.
             yield platform.Run(runnable, i)