[NoStatePrefetch] Fix the PrefetchAge histogram to match histograms.xml

chrome/browser/prerender/prerender_histograms.cc

Index: chrome/browser/prerender/prerender_histograms.cc
diff --git a/chrome/browser/prerender/prerender_histograms.cc b/chrome/browser/prerender/prerender_histograms.cc
index 60bf8349d832644b8078a03703ef5e0a6f443f68..d7ea7309607e65c57d8c91aa51bf9107d45037cc 100644
--- a/chrome/browser/prerender/prerender_histograms.cc
+++ b/chrome/browser/prerender/prerender_histograms.cc
@@ -468,10 +468,9 @@ void PrerenderHistograms::RecordPrefetchFirstContentfulPaintTime(
 
   if (!prefetch_age.is_zero()) {
     DCHECK_NE(origin, ORIGIN_NONE);
-    RecordHistogramTime(
-        GetHistogramName(origin, IsOriginWash(), "Prerender.PrefetchAge"),
-        base::TimeDelta::FromMilliseconds(10), base::TimeDelta::FromMinutes(30),
-        prefetch_age, 50);
+    RecordHistogramTime(GetHistogramName(origin, IsOriginWash(), "PrefetchAge"),
+                        base::TimeDelta::FromMilliseconds(10),
+                        base::TimeDelta::FromMinutes(30), prefetch_age, 50);
   }
 
   std::string histogram_base_name;