Add DocWrite.Block metric for NavigationToFirstContentfulPaint.

chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
index bc18f8eb87f25c0f75774b0cd1c503480e675f0b..3093232f15b017f2121c21b544a76ff0826b2ea6 100644
--- a/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
@@ -103,6 +103,9 @@ const char
         [] = "PageLoad.Clients.DocWrite.Evaluator.ParseTiming."
              "ParseBlockedOnScriptLoadFromDocumentWrite.Background";
 
+const char kHistogramDocWriteBlockFirstContentfulPaintImmediate[] =
+    "PageLoad.Clients.DocWrite.Block.PaintTiming."
+    "NavigationToFirstContentfulPaint";
 const char kHistogramDocWriteBlockParseStartToFirstContentfulPaintImmediate[] =
     "PageLoad.Clients.DocWrite.Block.PaintTiming."
     "ParseStartToFirstContentfulPaint";
@@ -299,6 +302,9 @@ void DocumentWritePageLoadMetricsObserver::
   if (WasStartedInForegroundEventInForeground(timing.first_contentful_paint,
                                               info)) {
     PAGE_LOAD_HISTOGRAM(
+        internal::kHistogramDocWriteBlockFirstContentfulPaintImmediate,
+        timing.first_contentful_paint);
+    PAGE_LOAD_HISTOGRAM(
         internal::
             kHistogramDocWriteBlockParseStartToFirstContentfulPaintImmediate,
         timing.first_contentful_paint - timing.parse_start);