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

chrome/renderer/mock_render_thread.h

Index: chrome/renderer/mock_render_thread.h
===================================================================
--- chrome/renderer/mock_render_thread.h	(revision 92822)
+++ chrome/renderer/mock_render_thread.h	(working copy)
@@ -83,8 +83,8 @@
   // False if the user decides to cancel.
   void set_print_dialog_user_response(bool response);
 
-  // Set to true to simulate canceling of a print preview.
-  void set_cancel_print_preview(bool cancel);
+  // Get the number of pages to generate for print preview.
+  int print_preview_pages_remaining();
 
  private:
   // This function operates as a regular IPC listener.
@@ -124,7 +124,8 @@
 
   void OnDidGetPrintedPagesCount(int cookie, int number_pages);
   void OnDidPrintPage(const PrintHostMsg_DidPrintPage_Params& params);
-  void OnDidPreviewPage(int page_number, bool* cancel);
+  void OnDidGetPreviewPageCount(int document_cookie, int number_pages);
+  void OnDidPreviewPage(int page_number);
 
   // For print preview, PrintWebViewHelper will update settings.
   void OnUpdatePrintSettings(int document_cookie,
@@ -152,8 +153,8 @@
   // True to simulate user clicking print. False to cancel.
   bool print_dialog_user_response_;
 
-  // True to simulate cancelling a print preview.
-  bool cancel_print_preview_;
+  // Number of pages to generate for print preview.
+  int print_preview_pages_remaining_;
 };
 
 #endif  // CHROME_RENDERER_MOCK_RENDER_THREAD_H_