Add support for tracking loading behavior of child frames.

chrome/renderer/page_load_metrics/page_timing_metrics_sender.cc

 // Copyright 2015 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.
 
 #include "chrome/renderer/page_load_metrics/page_timing_metrics_sender.h"
 
 #include <utility>
 
 #include "base/callback.h"
 #include "base/time/time.h"
@@ skipping 11 matching lines @@
 PageTimingMetricsSender::PageTimingMetricsSender(
     IPC::Sender* ipc_sender,
     int routing_id,
     std::unique_ptr<base::Timer> timer,
     const PageLoadTiming& initial_timing)
     : ipc_sender_(ipc_sender),
       routing_id_(routing_id),
       timer_(std::move(timer)),
       last_timing_(initial_timing),
       metadata_(PageLoadMetadata()) {
-  // Send an initial IPC relatively early to help track aborts.
-  EnsureSendTimer(kInitialTimerDelayMillis);
+  if (!initial_timing.IsEmpty()) {
+    // Send an initial IPC relatively early to help track aborts.
+    EnsureSendTimer(kInitialTimerDelayMillis);
+  }
 }
 
 // On destruction, we want to send any data we have if we have a timer
 // currently running (and thus are talking to a browser process)
 PageTimingMetricsSender::~PageTimingMetricsSender() {
   if (timer_->IsRunning()) {
     timer_->Stop();
     SendNow();
   }
 }
@@ skipping 28 matching lines @@
         FROM_HERE, base::TimeDelta::FromMilliseconds(delay),
         base::Bind(&PageTimingMetricsSender::SendNow, base::Unretained(this)));
 }
 
 void PageTimingMetricsSender::SendNow() {
   ipc_sender_->Send(new PageLoadMetricsMsg_TimingUpdated(
       routing_id_, last_timing_, metadata_));
 }
 
 }  // namespace page_load_metrics