Fix constrained_window_views guest view regression

This is a partial revert of
https://chromium-review.googlesource.com/c/chromium/src/+/1986918
which caused a chrome force-signin flow to crash.

Bug: 1076696, 1038584
Change-Id: I2148a18bd3d36700ade50b554511d580e2d73164
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633805Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845192}

chrome/browser/portal/portal_browsertest.cc

@@ -130,7 +130,11 @@ IN_PROC_BROWSER_TEST_F(
                 browser()->tab_strip_model()->GetActiveWebContents(), nullptr));
 }
 
-IN_PROC_BROWSER_TEST_F(PortalBrowserTest, HttpBasicAuthenticationInPortal) {
+// TODO(mcnee): Disabled due to the initial fix for this causing a regression.
+// See https://crbug.com/1076696 . Investigate the cause of this regression and
+// re-enable.
+IN_PROC_BROWSER_TEST_F(PortalBrowserTest,
+                       DISABLED_HttpBasicAuthenticationInPortal) {
   ASSERT_TRUE(embedded_test_server()->Start());
   GURL url(embedded_test_server()->GetURL("/title1.html"));
   ui_test_utils::NavigateToURL(browser(), url);

components/constrained_window/BUILD.gn

@@ -16,6 +16,7 @@ static_library("constrained_window") {
   ]
 
   deps = [
+    "//components/guest_view/browser",
     "//components/web_modal",
     "//content/public/browser",
     "//ui/display",

components/constrained_window/DEPS

 include_rules = [
+  "+components/guest_view/browser",
   "+components/web_modal",
   "+content/public/browser",
   "+ui/aura",

components/constrained_window/constrained_window_views.cc

@@ -12,6 +12,7 @@
 #include "base/no_destructor.h"
 #include "build/build_config.h"
 #include "components/constrained_window/constrained_window_views_client.h"
+#include "components/guest_view/browser/guest_view_base.h"
 #include "components/web_modal/web_contents_modal_dialog_host.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
 #include "components/web_modal/web_contents_modal_dialog_manager_delegate.h"
@@ -164,7 +165,10 @@ void UpdateWidgetModalDialogPosition(views::Widget* widget,
 
 content::WebContents* GetTopLevelWebContents(
     content::WebContents* initiator_web_contents) {
-  return initiator_web_contents->GetResponsibleWebContents();
+  // TODO(mcnee): Investigate why |WebContents::GetResponsibleWebContents| may
+  // return the wrong contents here.
+  return guest_view::GuestViewBase::GetTopLevelWebContents(
+      initiator_web_contents);
 }
 
 views::Widget* ShowWebModalDialogViews(