Android: Disallow iframes from requesting to auto-log-in.

Other embedded content, such as plug-ins, is also prevented from incurring
auto-log-in requests.

BUG=334230
TEST=You still get the auto-log-in infobar when the requesting site is the
top-level frame, but never otherwise.

Review URL: https://codereview.chromium.org/131483010

Cr-Commit-Position: refs/heads/master@{#299928}

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

@@ -642,8 +642,10 @@ void ChromeResourceDispatcherHostDelegate::OnResponseStarted(
   // See if the response contains the X-Auto-Login header.  If so, this was
   // a request for a login page, and the server is allowing the browser to
   // suggest auto-login, if available.
-  AutoLoginPrompter::ShowInfoBarIfPossible(request, info->GetChildID(),
-                                           info->GetRouteID());
+  if (info->IsMainFrame()) {
+    AutoLoginPrompter::ShowInfoBarIfPossible(request, info->GetChildID(),
+                                             info->GetRouteID());
+  }
 #endif
 
   ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);