Fix OOPIF-based <webview>.

content/common/site_isolation_policy.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/site_isolation_policy.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
+#include "content/public/common/browser_plugin_guest_mode.h"
 #include "content/public/common/browser_side_navigation_policy.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
 
 namespace content {
 
 // static
 bool SiteIsolationPolicy::AreCrossProcessFramesPossible() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
              switches::kSitePerProcess) ||
-         GetContentClient()->IsSupplementarySiteIsolationModeEnabled();
+         GetContentClient()->IsSupplementarySiteIsolationModeEnabled() ||
+         BrowserPluginGuestMode::UseCrossProcessFramesForGuests();
 }
 
 // static
 bool SiteIsolationPolicy::UseDedicatedProcessesForAllSites() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kSitePerProcess);
 }
 
 // static
 bool SiteIsolationPolicy::UseSubframeNavigationEntries() {
   // Enable the new navigation history behavior if any manner of site isolation
   // is active.
   // PlzNavigate: also enable the new navigation history behavior.
   return AreCrossProcessFramesPossible() || IsBrowserSideNavigationEnabled();
 }
 
 // static
 bool SiteIsolationPolicy::IsSwappedOutStateForbidden() {
   return true;
 }
 
 }  // namespace content