[Remote suggestions] Add DataUse.MessageSize suffixes.

This CL fixes a minor ommision in CL 2685523002.

BUG=688945

Review-Url: https://codereview.chromium.org/2726223003
Cr-Commit-Position: refs/heads/master@{#454684}
(cherry picked from commit 291cbdc)

Review-Url: https://codereview.chromium.org/2728333002 .
Cr-Commit-Position: refs/branch-heads/3029@{#16}
Cr-Branched-From: 939b32e-refs/heads/master@{#454471}

tools/metrics/histograms/histograms.xml

@@ -115081,7 +115081,13 @@ from previous Chrome versions.
   <suffix name="Autofill"/>
   <suffix name="Policy"/>
   <suffix name="SpellChecker"/>
-  <suffix name="NTPSnippets"/>
+  <suffix name="NTPSnippets">
+    <obsolete>
+      Deprecated March 2017
+    </obsolete>
+  </suffix>
+  <suffix name="NTPSnippetsSuggestions"/>
+  <suffix name="NTPSnippetsThumbnails"/>
   <affected-histogram name="DataUse.MessageSize"/>
 </histogram_suffixes>