Add .SingleTab and .MultiTabs suffix to Startup.FirstWebContents.MainNavigationStart histogram.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 778bde8307e04d91858887fe90fe838ec55fbd2d..e3c9f73f484031e0fc20ac5899e01518ab0e9cb6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -117761,6 +117761,10 @@ value.
   <affected-histogram name="Startup.FirstWebContents.MainFrameLoad2"/>
   <affected-histogram name="Startup.FirstWebContents.MainNavigationFinished"/>
   <affected-histogram name="Startup.FirstWebContents.MainNavigationStart"/>
+  <affected-histogram
+      name="Startup.FirstWebContents.MainNavigationStart.MultiTabs"/>
+  <affected-histogram
+      name="Startup.FirstWebContents.MainNavigationStart.SingleTab"/>
   <affected-histogram name="Startup.FirstWebContents.NonEmptyPaint"/>
   <affected-histogram name="Startup.FirstWebContents.NonEmptyPaint2"/>
   <affected-histogram name="Startup.LoadTime.ExeMainToDllMain"/>
@@ -117783,6 +117787,12 @@ value.
   <affected-histogram name="StartupTimeBomb.Alarm"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="StartupWorkload" separator=".">
+  <suffix name="SingleTab" label="Single tab instantiated on startup."/>
+  <suffix name="MultiTabs" label="Multiple tabs instantiated on startup."/>
+  <affected-histogram name="Startup.FirstWebContents.MainNavigationStart"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="Storage.BlobAppendableItems" separator=".">
   <suffix name="Bytes" label="Appending bytes."/>
   <suffix name="File" label="Appending a file with a known size."/>