Add metrics for RollbackSaveResult

- Adds enum histogram for RollbackSaveResult which represents the
result from attempting to save a users data during a rollback
- Emitting to this metric will happen via the ChromeOS Metrics Library

Bug: chromium:881341
Change-Id: I25991e754dd7186de63042222c38f94573d33bcb
Reviewed-on: https://chromium-review.googlesource.com/c/1416534
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623784}
diff --git a/tools/metrics/histograms/enums.xml b/tools/metrics/histograms/enums.xml
index d4d34d6..da4d3b94 100644
--- a/tools/metrics/histograms/enums.xml
+++ b/tools/metrics/histograms/enums.xml
@@ -45770,6 +45770,12 @@
   <int value="3" label="Stage 3 Failure"/>
 </enum>
 
+<enum name="Rollback_RollbackSaveResult">
+  <int value="0" label="Succeeded"/>
+  <int value="1" label="Stage 1 Failure"/>
+  <int value="2" label="Stage 2 Failure"/>
+</enum>
+
 <enum name="RSAKeyUsage">
   <int value="0" label="Not an RSA key"/>
   <int value="1" label="OK (no extension)"/>
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 527f842..b96bc2b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -94199,6 +94199,14 @@
   </summary>
 </histogram>
 
+<histogram name="Rollback.RollbackSaveResult"
+    enum="Rollback_RollbackSaveResult">
+  <owner>zentaro@chromium.org</owner>
+  <summary>
+    The result when attempting to save data during a Chrome OS rollback.
+  </summary>
+</histogram>
+
 <histogram name="SadTab.Created" enum="SadTabKind">
   <obsolete>
     Replaced with Tabs.SadTab.* in R20.