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 1fb91ed32081c5dfd22c5a8dfea0837e468c54c7..e9b54992953749fd657da326def12b5c6183031a 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";
@@ -311,6 +314,9 @@ void DocumentWritePageLoadMetricsObserver::
   if (WasStartedInForegroundOptionalEventInForeground(
           timing.first_contentful_paint, info)) {
     PAGE_LOAD_HISTOGRAM(
+        internal::kHistogramDocWriteBlockFirstContentfulPaintImmediate,
+        timing.first_contentful_paint.value());
+    PAGE_LOAD_HISTOGRAM(
         internal::
             kHistogramDocWriteBlockParseStartToFirstContentfulPaintImmediate,
         timing.first_contentful_paint.value() - timing.parse_start.value());