Add UMA histograms for the inter-process TimeTicks skew.

content/child/resource_dispatcher.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/child/resource_dispatcher.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
@@ skipping 767 matching lines @@
   RemoteToLocalTimeTicks(converter, &load_timing->proxy_resolve_end);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.dns_start);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.dns_end);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.connect_start);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.connect_end);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.ssl_start);
   RemoteToLocalTimeTicks(converter, &load_timing->connect_timing.ssl_end);
   RemoteToLocalTimeTicks(converter, &load_timing->send_start);
   RemoteToLocalTimeTicks(converter, &load_timing->send_end);
   RemoteToLocalTimeTicks(converter, &load_timing->receive_headers_end);
+
+  // Collect UMA on the inter-process skew.
+  if (converter.IsSkewAdditiveForMetrics()) {
+    UMA_HISTOGRAM_BOOLEAN(
+        "InterProcessTimeTicks.IsSkewAdditive_BrowserToRenderer", true);

[Alexei Svitkine (slow), 2014/08/15 16:54:33]

Nit: Extract the if condition outside the if into a local var and log this
histogram only once outside the loop. (Will reduce number of macro invocations,
since each one expands to a bunch of code and adds to the binary bloat.)

Same for the other code.

[ppi, 2014/08/18 09:29:04]

Done.

+    base::TimeDelta skew = converter.GetSkewForMetrics();
+    if (skew >= base::TimeDelta()) {
+      UMA_HISTOGRAM_TIMES(
+          "InterProcessTimeTicks.BrowserAhead_BrowserToRenderer", skew);
+    } else {
+      UMA_HISTOGRAM_TIMES(
+          "InterProcessTimeTicks.BrowserBehind_BrowserToRenderer", -skew);
+    }
+  } else {
+    UMA_HISTOGRAM_BOOLEAN(
+        "InterProcessTimeTicks.IsSkewAdditive_BrowserToRenderer", false);
+  }
 }
 
 base::TimeTicks ResourceDispatcher::ToRendererCompletionTime(
     const PendingRequestInfo& request_info,
     const base::TimeTicks& browser_completion_time) const {
   if (request_info.completion_time.is_null()) {
     return browser_completion_time;
   }
 
   // TODO(simonjam): The optimal lower bound should be the most recent value of
@@ skipping 62 matching lines @@
 void ResourceDispatcher::ReleaseResourcesInMessageQueue(MessageQueue* queue) {
   while (!queue->empty()) {
     IPC::Message* message = queue->front();
     ReleaseResourcesInDataMessage(*message);
     queue->pop_front();
     delete message;
   }
 }
 
 }  // namespace content