FirstMeaningfulPaint UMA: Reduce the network activity threshold

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

 // Copyright (c) 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 "base/macros.h"
 #include "base/test/histogram_tester.h"
 #include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "chrome/browser/page_load_metrics/observers/aborts_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.h"
@@ skipping 370 matching lines @@
 }
 
 IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest,
                        FirstMeaningfulPaintRecorded) {
   ASSERT_TRUE(embedded_test_server()->Start());
 
   ui_test_utils::NavigateToURL(browser(),
                                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)",
       kNetworkIdleTime + kMargin);
   bool result;
   EXPECT_TRUE(content::ExecuteScriptAndExtractBool(
       browser()->tab_strip_model()->GetActiveWebContents(),
       javascript, &result));
   EXPECT_TRUE(result);
 
@@ skipping 18 matching lines @@
   NavigateToUntrackedUrl();
 
   histogram_tester_.ExpectUniqueSample(
       internal::kHistogramFirstMeaningfulPaintStatus,
       internal::FIRST_MEANINGFUL_PAINT_DID_NOT_REACH_NETWORK_STABLE, 1);
   histogram_tester_.ExpectTotalCount(
       internal::kHistogramFirstMeaningfulPaint, 0);
   histogram_tester_.ExpectTotalCount(
       internal::kHistogramParseStartToFirstMeaningfulPaint, 0);
 }