Added LeastUsedAccountDays metric

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 b007c1a70e91623132286c3dc08a4d70770f6015..768cab691849d3ae2b4051248a5b0b38e30d28dd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5179,6 +5179,13 @@ other types of suffix sets.
   <summary>Chrome OS login failure reason.</summary>
 </histogram>
 
+<histogram name="Login.LeastUsedAccountDays" units="days">
+  <summary>
+    Chrome OS histogram that keeps track of the days since the least frequently
+    used account signed in. Reported on every boot and once a day after that.
+  </summary>
+</histogram>
+
 <histogram name="Login.PolicyFilesStatePerBoot" enum="LoginPolicyFilesState">
   <summary>The state of Chrome OS owner key and device policy files.</summary>
 </histogram>
@@ -10428,6 +10435,13 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Platform.DiskUsage.LeastUsedAccountDays" units="days">
+  <summary>
+    Days since the least frequently used account signed in. Logged once a day,
+    if disk usage is high.
+  </summary>
+</histogram>
+
 <histogram name="Platform.DiskUsage.NumUserHomeDirectories"
     units="home directories">
   <summary>
@@ -24558,6 +24572,7 @@ other types of suffix sets.
   <affected-histogram name="Platform.DiskUsage.Downloads_Max"/>
   <affected-histogram name="Platform.DiskUsage.GCache_Avg"/>
   <affected-histogram name="Platform.DiskUsage.GCache_Max"/>
+  <affected-histogram name="Platform.DiskUsage.LeastUsedAccountDays"/>
 </fieldtrial>
 
 <fieldtrial name="DnsImpact2">