Revert "Disable HTTP auth committed interstitials by default"

This reverts commit 060c246f7f4d1b3dae5c9bf930430de118facc85.

Reason for revert: A blocker bug has been fixed, so this revert re-enables HTTP auth committed interstitials on ToT.

Original change's description:
> Disable HTTP auth committed interstitials by default
>
> Committed interstitials for HTTP auth renders the 401 body underneath
> the auth prompt. This has proven to be problematic in some cases (see
> bug). This CL disables committed interstitials for HTTP auth by
> default while I work on a fix for avoiding rendering the 401 body.
>
> Bug: 992639
> Change-Id: I63195a66c4ad81452e24d260afdc7dd938eab769
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1756638
> Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
> Commit-Queue: Emily Stark <estark@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#687695}

TBR=vasilii@chromium.org,estark@chromium.org

Bug: 992639
Change-Id: I8c31e07ab4ea2ab70bd4f7006a0d19970d7f7d34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1801057
Reviewed-by: Emily Stark <estark@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#696096}
diff --git a/chrome/browser/password_manager/password_manager_browsertest.cc b/chrome/browser/password_manager/password_manager_browsertest.cc
index 3780e59..bea7e2a 100644
--- a/chrome/browser/password_manager/password_manager_browsertest.cc
+++ b/chrome/browser/password_manager/password_manager_browsertest.cc
@@ -34,7 +34,6 @@
 #include "chrome/browser/ui/passwords/manage_passwords_ui_controller.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/test/test_browser_dialog.h"
-#include "chrome/common/chrome_features.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/ui_test_utils.h"
@@ -1411,10 +1410,6 @@
 // a new tab with a URL for which the embedded test server issues a basic auth
 // challenge.
 IN_PROC_BROWSER_TEST_F(PasswordManagerBrowserTest, NoLastLoadGoodLastLoad) {
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeature(
-      ::features::kHTTPAuthCommittedInterstitials);
-
   // We must use a new test server here because embedded_test_server() is
   // already started at this point and adding the request handler to it would
   // not be thread safe.
@@ -2918,10 +2913,6 @@
 }
 
 IN_PROC_BROWSER_TEST_F(PasswordManagerBrowserTest, ProxyAuthFilling) {
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeature(
-      ::features::kHTTPAuthCommittedInterstitials);
-
   GURL test_page = embedded_test_server()->GetURL("/auth-basic");
 
   // Save credentials for "testrealm" in the store.
@@ -3605,9 +3596,6 @@
 // password manager works even though it should be disabled on the previous
 // page.
 IN_PROC_BROWSER_TEST_F(PasswordManagerBrowserTest, CorrectEntryForHttpAuth) {
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeature(
-      ::features::kHTTPAuthCommittedInterstitials);
     // The embedded_test_server() is already started at this point and adding
     // the request handler to it would not be thread safe. Therefore, use a new
     // server.
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index e84e44f..80fe567 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -411,7 +411,7 @@
 // Enables committed error pages instead of transient navigation entries for
 // HTTP auth interstitial pages (i.e. HTTP auth prompts initiated cross-origin).
 const base::Feature kHTTPAuthCommittedInterstitials{
-    "HTTPAuthCommittedInterstitials", base::FEATURE_DISABLED_BY_DEFAULT};
+    "HTTPAuthCommittedInterstitials", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables navigation suggestions UI for lookalike URLs (e.g. internationalized
 // domain names that are visually similar to popular domains or to domains with