Add missing Security histograms to histograms.xml

This adds three missing histograms to histograms.xml that should have
been introduced in https://crrev.com/c/914468: two enums,
Security.SecurityLevel.OnCommit and Security.SecurityLevel.OnComplete,
and one suffixed histogram, Security.TimeOnPage.

Bug: 803540
Change-Id: I608604067c422703efa130dbc16f271529d0bbf6
Reviewed-on: https://chromium-review.googlesource.com/949608
Commit-Queue: Christopher Thompson <cthomp@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540945}

tools/metrics/histograms/histograms.xml

@@ -80415,6 +80415,27 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Security.SecurityLevel.OnCommit" enum="SecurityLevel">
+  <owner>cthomp@chromium.org</owner>
+  <summary>
+    Records the security level of a page at the time the navigation commits.
+    Note that the security level of a page can change after commit time, so this
+    histogram should often be compared against
+    Security.SecurityLevel.OnComplete.
+  </summary>
+</histogram>
+
+<histogram name="Security.SecurityLevel.OnComplete" enum="SecurityLevel">
+  <owner>cthomp@chromium.org</owner>
+  <summary>
+    Records the security level of a page at the end of the page visit (i.e.,
+    navigating away from the page, reloading the page, clicking a link, closing
+    the tab, etc.). Note that this security level can be different than the
+    initial security level of the page, so this histogram should often be
+    compared against Security.SecuritLevel.OnCommit.
+  </summary>
+</histogram>
+
 <histogram base="true" name="Security.SiteEngagement">
   <owner>cthomp@chromium.org</owner>
   <summary>
@@ -80436,6 +80457,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="Security.TimeOnPage">
+  <owner>cthomp@chromium.org</owner>
+  <summary>
+    Records the time spent on the page (the time that the page was in the
+    foreground from the start of the navigation to the page visit completing due
+    to a new navigation or the tab being closed). This aggregates all foreground
+    time over the entire visit (multiple times in the foreground are added
+    together).
+  </summary>
+</histogram>
+
 <histogram name="Security.TreatInsecureOriginAsSecure">
   <owner>mkwst@chromium.org</owner>
   <summary>
@@ -113102,6 +113134,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <affected-histogram name="Security.PageEndReason"/>
   <affected-histogram name="Security.SiteEngagement"/>
   <affected-histogram name="Security.SiteEngagementDelta"/>
+  <affected-histogram name="Security.TimeOnPage"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="ServiceWorker.ContextRequestType" separator=".">