Revert of Remove stale RFHM check now that unload runs in the background.

content/browser/frame_host/render_frame_host_manager.cc

 // Copyright 2013 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/browser/frame_host/render_frame_host_manager.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 262 matching lines @@
 }
 
 bool RenderFrameHostManager::ShouldCloseTabOnUnresponsiveRenderer() {
   if (!cross_navigation_pending_)
     return true;
 
   // We should always have a pending RFH when there's a cross-process navigation
   // in progress.  Sanity check this for http://crbug.com/276333.
   CHECK(pending_render_frame_host_);
 
-  // Unload handlers run in the background, so we should never get an
-  // unresponsiveness warning for them.
-  CHECK(!render_frame_host_->IsWaitingForUnloadACK());
-
-  // If the tab becomes unresponsive during beforeunload while doing a
+  // If the tab becomes unresponsive during {before}unload while doing a
   // cross-site navigation, proceed with the navigation.  (This assumes that
   // the pending RenderFrameHost is still responsive.)
-  if (render_frame_host_->is_waiting_for_beforeunload_ack()) {
+  if (render_frame_host_->IsWaitingForUnloadACK()) {
+    // The request has been started and paused while we're waiting for the
+    // unload handler to finish.  We'll pretend that it did.  The pending
+    // renderer will then be swapped in as part of the usual DidNavigate logic.
+    // (If the unload handler later finishes, this call will be ignored because
+    // the pending_nav_params_ state will already be cleaned up.)
+    current_frame_host()->OnSwappedOut();
+  } else if (render_frame_host_->is_waiting_for_beforeunload_ack()) {
     // Haven't gotten around to starting the request, because we're still
     // waiting for the beforeunload handler to finish.  We'll pretend that it
     // did finish, to let the navigation proceed.  Note that there's a danger
     // that the beforeunload handler will later finish and possibly return
     // false (meaning the navigation should not proceed), but we'll ignore it
     // in this case because it took too long.
     if (pending_render_frame_host_->are_navigations_suspended()) {
       pending_render_frame_host_->SetNavigationsSuspended(
           false, base::TimeTicks::Now());
     }
@@ skipping 1404 matching lines @@
 void RenderFrameHostManager::DeleteRenderFrameProxyHost(
     SiteInstance* instance) {
   RenderFrameProxyHostMap::iterator iter = proxy_hosts_.find(instance->GetId());
   if (iter != proxy_hosts_.end()) {
     delete iter->second;
     proxy_hosts_.erase(iter);
   }
 }
 
 }  // namespace content