Removing Variations support for google_update_experiment_id.

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 55e604900df4a4e0e3fe78de7604ef08b4e4f7c7..126f94ce9249dfba98b59d4843673fd9c91a534e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -68148,6 +68148,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Variations.GoogleUpdateRegistryLabelsNeedClearing"
+    enum="BooleanNeedsClearing">
+  <owner>jwd@chromium.org</owner>
+  <summary>
+    If the registry value for Google Update experiment labels contains
+    Variations experiments, and therefore needs to have them cleared. This will
+    be recorderd once per sessions, right before attempting to clear the value.
+  </summary>
+</histogram>
+
 <histogram name="Variations.HeaderConstructionTime" units="microseconds">
   <owner>asvitkine@chromium.org</owner>
   <summary>How long it took to create the X-Client-Data header.</summary>
@@ -74930,6 +74940,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Missing data in disk cache"/>
 </enum>
 
+<enum name="BooleanNeedsClearing" type="int">
+  <int value="0" label="Doesn't need clearing"/>
+  <int value="1" label="Needs to be clearred"/>
+</enum>
+
 <enum name="BooleanNullStream" type="int">
   <int value="0" label="Stream is not a nullptr"/>
   <int value="1" label="Stream is a nullptr"/>