Don't swap out the old RenderFrameHost until the new one commits.

content/common/view_messages.h

 // Copyright (c) 2012 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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 600 matching lines @@
 IPC_MESSAGE_ROUTED0(ViewMsg_WasHidden)
 
 // Tells the render view that it is no longer hidden (see WasHidden), and the
 // render view is expected to respond with a full repaint if needs_repainting
 // is true. If needs_repainting is false, then this message does not trigger a
 // message in response.
 IPC_MESSAGE_ROUTED2(ViewMsg_WasShown,
                     bool /* needs_repainting */,
                     ui::LatencyInfo /* latency_info */)
 
-// Sent to inform the view that it was swapped out.  This allows the process to
-// exit if no other views are using it.
-IPC_MESSAGE_ROUTED0(ViewMsg_WasSwappedOut)
-
 // Tells the renderer to focus the first (last if reverse is true) focusable
 // node.
 IPC_MESSAGE_ROUTED1(ViewMsg_SetInitialFocus,
                     bool /* reverse */)
 
 // Sent to inform the renderer to invoke a context menu.
 // The parameter specifies the location in the render view's coordinates.
 IPC_MESSAGE_ROUTED2(ViewMsg_ShowContextMenu,
                     ui::MenuSourceType,
                     gfx::Point /* location where menu should be shown */)
@@ skipping 1059 matching lines @@
 // Since the browser keeps handles to the allocated transport DIBs, this
 // message is sent to tell the browser that it may release them when the
 // renderer is finished with them.
 IPC_MESSAGE_CONTROL1(ViewHostMsg_FreeTransportDIB,
                      TransportDIB::Id /* DIB id */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.