Make EDU Coexistence WebUI handle redirection to flow finish page

Previously we were only doing this when running the flow from a local
workstation. However, it appears that the "continue" URL parameter on
accounts.google.com isn't working.  It's not yet clear if this is a
recently changed behavior, or
if it never worked.

In the meantime, this fixes the issue with the flow not being able
to complete on the production servers because of the non-functional
continue URL parameter.

Bug: 1160168
Change-Id: Ide9b02d3eca7061fa86803eaf0a74cf6dbe391ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2597074Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Commit-Queue: Dan S <danan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838948}

chrome/browser/resources/chromeos/edu_coexistence/edu_coexistence_controller.js

@@ -214,14 +214,13 @@ export class EduCoexistenceController extends PostMessageAPIServer {
     this.userInfo_ = e.detail;
     this.browserProxy_.completeLogin(e.detail);
 
-    // GAIA pages don't allow localhost as a "continue" URL, so we have to
-    // manually update the src when doing development against a localhost-hosted
-    // test server.
-    if (this.flowURL_.hostname === 'localhost') {
-      let finishURL = this.flowURL_;
-      finishURL.pathname = '/supervision/coexistence/finish';
-      this.webview_.src = finishURL.toString();
-    }
+    // The EDU Signin page doesn't appear to use the "continue" URL, so we have
+    // to manually update the src to continue to the last page of the flow.
+    // TODO(crbug.com/1160166): Investigate why the "continue" parameter doesn't
+    // work for EDU signin on accounts.google.com.
+    let finishURL = this.flowURL_;
+    finishURL.pathname = '/supervision/coexistence/finish';
+    this.webview_.src = finishURL.toString();
   }
 
   /**