Prevent modal dialogs when preparing to swap out.

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 1140 matching lines @@
 // When a renderer sends a ViewHostMsg_Focus to the browser process,
 // the browser has the option of sending a ViewMsg_CantFocus back to
 // the renderer.
 IPC_MESSAGE_ROUTED0(ViewMsg_CantFocus)
 
 // Instructs the renderer to invoke the frame's shouldClose method, which
 // runs the onbeforeunload event handler.  Expects the result to be returned
 // via ViewHostMsg_ShouldClose.
 IPC_MESSAGE_ROUTED0(ViewMsg_ShouldClose)
 
+// Tells the renderer to suppress any further modal dialogs until it receives a
+// corresponding ViewMsg_SwapOut message.  This ensures that no
+// PageGroupLoadDeferrer is on the stack for SwapOut.
+IPC_MESSAGE_ROUTED0(ViewMsg_SuppressDialogsUntilSwapOut)
+
 // Instructs the renderer to swap out for a cross-site transition, including
 // running the unload event handler. Expects a SwapOut_ACK message when
 // finished.
 IPC_MESSAGE_ROUTED0(ViewMsg_SwapOut)
 
 // Instructs the renderer to close the current page, including running the
 // onunload event handler.
 //
 // Expects a ClosePage_ACK message when finished.
 IPC_MESSAGE_ROUTED0(ViewMsg_ClosePage)
@@ skipping 1194 matching lines @@
 // synchronously (see crbug.com/120597). This IPC message sends the character
 // bounds after every composition change to always have correct bound info.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 #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.