FirstMeaningfulPaint UMA: Reduce the network activity threshold

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
index f766b71b7986b4fafaaa3df9660b378f5d7e2943..da90bfdecd54ca33b658011e95e61121c0541131 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
@@ -388,7 +388,7 @@ IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest,
                                embedded_test_server()->GetURL("/title1.html"));
 
   // Wait until the renderer finishes observing layouts.
-  const int kNetworkIdleTime = 2000;
+  const int kNetworkIdleTime = 500;
   const int kMargin = 500;
   const std::string javascript = base::StringPrintf(
       "setTimeout(() => window.domAutomationController.send(true), %d)",