Add Histogram for currentURLWithTrustLevel removal.

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 922fdc96535588c2b4c8f74a3837079b58fc8921..b47f8c6a11a266ad92536de9e5581321fafbf027 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -60881,6 +60881,20 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Web.CurrentURLEqualsLastCommittedURL" enum="BooleanEqual">
+  <owner>michaeldo@chromium.com</owner>
+  <summary>
+    [iOS] Reports URL matches between the return value from the WebState's
+    GetLastCommittedURL and GetCurrentURL methods. It is expected the values
+    will be equal to confirm that GetCurrentURL can now be replaced with
+    GetLastCommittedURL. This will be called each time WebStateImpl::
+    GetCurrentURL(URLVerificationTrustLevel* trust_level) is called, which is an
+    old method of obtaining the url and trust level. The trust level was only
+    relevant with UIWebView, so this method is only called from code which has
+    not yet been updated since UIWebView was removed.
+  </summary>
+</histogram>
+
 <histogram name="Webapp.Splashscreen.BackgroundColor"
     enum="SplashscreenColorStatus">
   <owner>mlamouri@chromium.org</owner>
@@ -65961,6 +65975,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Enabled"/>
 </enum>
 
+<enum name="BooleanEqual" type="int">
+  <int value="0" label="Not Equal"/>
+  <int value="1" label="Equal"/>
+</enum>
+
 <enum name="BooleanError" type="int">
   <int value="0" label="No Error"/>
   <int value="1" label="Error"/>