Add cryptohome out-of-process mount metrics.

Metrics were added in https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1958504.
Enums were added in https://chromium-review.googlesource.com/c/chromium/src/+/1976310.

BUG=985492
TEST=validate_format.py, pretty_print.py.

Change-Id: I9ed97d931fbe7877b7d1deb33a5426e9ef8c4011
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976436
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Christopher Thompson <cthomp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726565}

tools/metrics/histograms/histograms.xml

@@ -29586,6 +29586,26 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Cryptohome.OOPMountCleanupResult"
+    enum="CryptohomeOOPMountCleanupResult" expires_after="2021-02-01">
+  <owner>betuls@chromium.org</owner>
+  <owner>jorgelo@chromium.org</owner>
+  <summary>
+    The result of a cryptohome out-of-process mount cleanup. Recorded once per
+    logout.
+  </summary>
+</histogram>
+
+<histogram name="Cryptohome.OOPMountOperationResult"
+    enum="CryptohomeOOPMountOperationResult" expires_after="2021-02-01">
+  <owner>betuls@chromium.org</owner>
+  <owner>jorgelo@chromium.org</owner>
+  <summary>
+    The result of a cryptohome out-of-process mount operation. Recorded once per
+    login attempt.
+  </summary>
+</histogram>
+
 <histogram name="Cryptohome.ParallelTasks" units="count"
     expires_after="2021-01-01">
   <owner>zuan@chromium.org</owner>