Remove old default search preferences.

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 4dcf9c0041323ce6d4908f9474600c8af2cbd995..c4eb05f46030ab0b0d56a427c74e2abd6e3177f9 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -58847,6 +58847,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Search.MigratedPrefToDictionaryValue" enum="BooleanHit">
+  <obsolete>
+    Deprecated after migrator is deleted in 12/2016.
+  </obsolete>
   <owner>caitkp@chromium.org</owner>
   <summary>
     The number of times that a user-selected DSE was migrated from separate
@@ -106274,9 +106277,9 @@ value.
   <int value="5" label="extensions::pref_names::kExtensions"/>
   <int value="6" label="kGoogleServicesLastUsername"/>
   <int value="7" label="kSearchProviderOverrides"/>
-  <int value="8" label="kDefaultSearchProviderSearchURL"/>
-  <int value="9" label="kDefaultSearchProviderKeyword"/>
-  <int value="10" label="kDefaultSearchProviderName"/>
+  <int value="8" label="kDefaultSearchProviderSearchURL (Obsolete 12/2016)"/>
+  <int value="9" label="kDefaultSearchProviderKeyword (Obsolete 12/2016)"/>
+  <int value="10" label="kDefaultSearchProviderName (Obsolete 12/2016)"/>
   <int value="11" label="kPinnedTabs"/>
   <int value="12" label="kKnownDisabled (Obsolete 07/2014)"/>
   <int value="13" label="kProfileResetPromptMemento (Obsolete 11/2015)"/>