Make RequestMetrics take a raw time rather than a clock

... which is going to make it easier to move around.

synapse/http/request_metrics.py

@@ -100,12 +100,12 @@ response_size = metrics.register_counter(
 
 
 class RequestMetrics(object):
-    def start(self, clock, name):
+    def start(self, time_msec, name):
-        self.start = clock.time_msec()
+        self.start = time_msec
         self.start_context = LoggingContext.current_context()
         self.name = name
 
-    def stop(self, clock, request):
+    def stop(self, time_msec, request):
         context = LoggingContext.current_context()
 
         tag = ""
@@ -122,7 +122,7 @@ class RequestMetrics(object):
         response_count.inc(request.method, self.name, tag)
 
         response_timer.inc_by(
-            clock.time_msec() - self.start, request.method,
+            time_msec - self.start, request.method,
             self.name, tag
         )
 

synapse/http/server.py

@@ -87,7 +87,7 @@ def wrap_request_handler(request_handler, include_metrics=False):
                 # JsonResource (or a subclass), and JsonResource._async_render
                 # will update it once it picks a servlet.
                 servlet_name = self.__class__.__name__
-                request_metrics.start(self.clock, name=servlet_name)
+                request_metrics.start(self.clock.time_msec(), name=servlet_name)
 
                 with request.processing():
                     try:
@@ -138,7 +138,7 @@ def wrap_request_handler(request_handler, include_metrics=False):
                     finally:
                         try:
                             request_metrics.stop(
-                                self.clock, request
+                                self.clock.time_msec(), request
                             )
                         except Exception as e:
                             logger.warn("Failed to stop metrics: %r", e)