Print Preview: Make preview generation event driven to eliminate synchronous messages.

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 "base/values.h"
 #include "base/shared_memory.h"
 #include "ipc/ipc_message_macros.h"
@@ skipping 152 matching lines @@
 
 // Tells the render view to switch the CSS to print media type, renders every
 // requested pages for print preview using the given |settings|. This gets
 // called multiple times as the user updates settings.
 IPC_MESSAGE_ROUTED1(PrintMsg_PrintPreview,
                     DictionaryValue /* settings */)
 
 // Tells a renderer to stop blocking script initiated printing.
 IPC_MESSAGE_ROUTED0(PrintMsg_ResetScriptedPrintCount)
 
+// Tells a renderer to continue generating the print preview.
+IPC_MESSAGE_ROUTED0(PrintMsg_ContinuePreview)
+
+// Tells a renderer to abort the print preview and reset all state.
+IPC_MESSAGE_ROUTED0(PrintMsg_AbortPreview)
 
 // 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 44 matching lines @@
                             base::FileDescriptor /* temp file fd */,
                             int /* fd in browser*/)
 IPC_MESSAGE_CONTROL1(PrintHostMsg_TempFileForPrintingWritten,
                      int /* fd in browser */)
 #endif
 
 // Asks the browser to do print preview.
 IPC_MESSAGE_ROUTED0(PrintHostMsg_RequestPrintPreview)
 
 // Notify the browser the number of pages in the print preview document.
-IPC_MESSAGE_ROUTED1(PrintHostMsg_DidGetPreviewPageCount,
+IPC_MESSAGE_ROUTED2(PrintHostMsg_DidGetPreviewPageCount,
+                    int  /* document cookie */,
                     int  /* page count */)
 
 // Notify the browser a print preview page has been rendered. Give the browser
 // a chance to cancel the print preview as needed. Page number is zero-based,
 // and can be -1 if it is just a check.
-IPC_SYNC_MESSAGE_ROUTED1_1(PrintHostMsg_DidPreviewPage,
-                           int  /* page number */,
-                           bool /* print preview cancelled */)
+IPC_MESSAGE_ROUTED1(PrintHostMsg_DidPreviewPage,
+                    int  /* page number */)
 
-// Sends back to the browser the rendered "printed document" for preview that
-// was requested by a PrintMsg_PrintPreview message. The memory handle in this
-// message is already valid in the browser process.
+// Sends back to the browser the complete rendered document for print preview
+// that was requested by a PrintMsg_PrintPreview message. The memory handle in
+// this message is already valid in the browser process.
 IPC_MESSAGE_ROUTED1(PrintHostMsg_PagesReadyForPreview,
                     PrintHostMsg_DidPreviewDocument_Params /* params */)
 
 // Tell the browser printing failed.
 IPC_MESSAGE_ROUTED1(PrintHostMsg_PrintingFailed,
                     int /* document cookie */)
 
 // Tell the browser print preview failed.
 IPC_MESSAGE_ROUTED1(PrintHostMsg_PrintPreviewFailed,
                     int /* document cookie */)
-
-// Tell the browser print preview was cancelled.
-IPC_MESSAGE_ROUTED1(PrintHostMsg_PrintPreviewCancelled,
-                    int /* document cookie */)