UKM Page load metrics observer: Fix crash when logging load timing

Fix crash when logging resource load timing metrics for the
main frame request in UKM page load metrics observer.

This is a tentative fix.

Change-Id: I70358e646fd64cad6e9e8258bec7c43c51633d78
Bug: 894789
TBR: bmcquade@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/1279942
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599862}

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc

@@ -285,8 +285,6 @@ void UkmPageLoadMetricsObserver::ReportMainResourceTimingMetrics(
   DCHECK_LE(dns_end_ms, connect_start_ms);
   DCHECK_LE(dns_start_ms, connect_start_ms);
   DCHECK_LE(connect_start_ms, connect_end_ms);
-  DCHECK_LE(connect_end_ms, send_start_ms);
-  DCHECK_LE(send_start_ms, receive_headers_end_ms);
 
   int64_t dns_duration_ms = dns_end_ms - dns_start_ms;
   int64_t connect_duration_ms = connect_end_ms - connect_start_ms;
@@ -298,10 +296,14 @@ void UkmPageLoadMetricsObserver::ReportMainResourceTimingMetrics(
 
   builder->SetMainFrameResource_DNSDelay(dns_duration_ms);
   builder->SetMainFrameResource_ConnectDelay(connect_duration_ms);
+  if (request_start_to_send_start_ms >= 0) {
     builder->SetMainFrameResource_RequestStartToSendStart(
         request_start_to_send_start_ms);
+  }
+  if (send_start_to_receive_headers_end_ms >= 0) {
     builder->SetMainFrameResource_SendStartToReceiveHeadersEnd(
         send_start_to_receive_headers_end_ms);
+  }
   builder->SetMainFrameResource_RequestStartToReceiveHeadersEnd(
       request_start_to_receive_headers_end_ms);
 }