Remove expired histogram: ChromeOS.GAIA.AuthenticatorContentWindowNull

Bug: 1088682
Change-Id: I7d4f647befb2e5b6a99442612e63ab7351e64522
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495268
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822218}

chrome/browser/resources/gaia_auth_host/authenticator.js

@@ -1240,13 +1240,6 @@ cr.define('cr.login', function() {
           console.error('Authenticator: contentWindow is null.');
         }
 
-        if (this.authMode == AuthMode.DEFAULT) {
-          chrome.send('metricsHandler:recordBooleanHistogram', [
-            'ChromeOS.GAIA.AuthenticatorContentWindowNull',
-            !this.webview_.contentWindow
-          ]);
-        }
-
         this.fireReadyEvent_();
         // Focus webview after dispatching event when webview is already
         // visible.

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

@@ -59,7 +59,6 @@
 #include "chrome/browser/ui/webui/chromeos/login/signin_fatal_error_screen_handler.h"
 #include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 #include "chrome/browser/ui/webui/chromeos/login/user_creation_screen_handler.h"
-#include "chrome/browser/ui/webui/metrics_handler.h"
 #include "chrome/browser/ui/webui/signin/signin_utils.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/chrome_features.h"
@@ -743,8 +742,6 @@ void GaiaScreenHandler::RegisterMessages() {
               &GaiaScreenHandler::HandleSecurityTokenPinEntered);
   AddCallback("onFatalError", &GaiaScreenHandler::HandleOnFatalError);
 
-  // Allow UMA metrics collection from JS.
-  web_ui()->AddMessageHandler(std::make_unique<MetricsHandler>());
   BaseScreenHandler::RegisterMessages();
 }
 

tools/metrics/histograms/histograms_xml/chromeos/histograms.xml

@@ -333,6 +333,9 @@ incoming reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="ChromeOS.GAIA.AuthenticatorContentWindowNull" enum="Boolean"
     expires_after="M85">
+  <obsolete>
+    Removed 2020-10.
+  </obsolete>
   <owner>wjmaclean@chromium.org</owner>
   <summary>
     Whether the GAIA Authenticator unexpectedly encountered a null contentWindow