Refine tracking of snippet dismissals.

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 381a91d009c797413fa8b733941e69861cd591a4..3b8cd7da25781a1898fec48f880ecad64bfdf8a7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -83964,7 +83964,9 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="0" label="Snippets were shown to the user"/>
   <int value="1" label="User scrolled through the snippets"/>
   <int value="2" label="User clicked on a snippet into the host website"/>
-  <int value="3" label="User swiped a snippet away"/>
+  <int value="3" label="User swiped a snippet away (obsolete)"/>
+  <int value="4" label="User swiped a snippet away after visiting"/>
+  <int value="5" label="User swiped a snippet away without visiting"/>
 </enum>
 
 <enum name="SocketStreamConnectionType" type="int">