perf: pass limits as a function argument

The function applying the limit has no access to the configuration. Therefore,
some higher layer will have to pass it as argument.

We do this in an independent change to clarify the next change.

contrib/perf.py

@@ -322,7 +322,8 b' DEFAULTLIMITS = ('
     (10.0, 3),
 )
 
-def _timer(fm, func, setup=None, title=None, displayall=False):
+def _timer(fm, func, setup=None, title=None, displayall=False,
+           limits=DEFAULTLIMITS):
     gc.collect()
     results = []
     begin = util.timer()
@@ -338,7 +339,7 b' def _timer(fm, func, setup=None, title=N'
         cstop = util.timer()
         # Look for a stop condition.
         elapsed = cstop - begin
-        for t, mincount in DEFAULTLIMITS:
+        for t, mincount in limits:
             if elapsed >= t and count >= mincount:
                 keepgoing = False
                 break