Print Preview: Make print preview tab modal.

chrome/common/print_messages.h

 // Copyright (c) 2011 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 printing.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 266 matching lines @@
 // called multiple times as the user updates settings.
 IPC_MESSAGE_ROUTED1(PrintMsg_PrintPreview,
                     DictionaryValue /* settings */)
 
 // Like PrintMsg_PrintPages, but using the print preview document's frame/node.
 IPC_MESSAGE_ROUTED0(PrintMsg_PrintForSystemDialog)
 
 // Tells a renderer to stop blocking script initiated printing.
 IPC_MESSAGE_ROUTED0(PrintMsg_ResetScriptedPrintCount)
 
+// Tells a renderer print preview has finished so it can exit its nested loop.
+IPC_MESSAGE_ROUTED0(PrintMsg_PrintPreviewDone)
+
 // Messages sent from the renderer to the browser.
 
 #if defined(OS_WIN)
 // Duplicates a shared memory handle from the renderer to the browser. Then
 // the renderer can flush the handle.
 IPC_SYNC_MESSAGE_ROUTED1_1(PrintHostMsg_DuplicateSection,
                            base::SharedMemoryHandle /* renderer handle */,
                            base::SharedMemoryHandle /* browser handle */)
 #endif
 
@@ skipping 84 matching lines @@
 
 // Tell the browser print preview was cancelled.
 IPC_MESSAGE_ROUTED1(PrintHostMsg_PrintPreviewCancelled,
                     int /* document cookie */)
 
 // Tell the browser print preview found the selected printer has invalid
 // settings (which typically caused by disconnected network printer or printer
 // driver is bogus).
 IPC_MESSAGE_ROUTED1(PrintHostMsg_PrintPreviewInvalidPrinterSettings,
                     int /* document cookie */)