[printing] Clean up PrintMockRenderThread::OnDidGetPrintedPagesCount

This CL cleans up the unused OnDidGetPrintedPagesCount which was
a handler for PrintHostMsg_DidGetPrintedPagesCount from
PrintMockRenderThread. The PrintHostMsg_DidGetPrintedPagesCount
message has been converted to Mojo [1] and the handler is not used
anymore.

[1] https://crrev.com/c/2326857

Bug: 1008939
Change-Id: Ifec8922958de92d544444d63198f22987a931aac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362070Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Julie Kim <jkim@igalia.com>
Cr-Commit-Position: refs/heads/master@{#799555}

components/printing/test/print_mock_render_thread.cc

@@ -86,11 +86,6 @@ void PrintMockRenderThread::OnScriptedPrint(
   }
 }
 
-void PrintMockRenderThread::OnDidGetPrintedPagesCount(int cookie,
-                                                      int number_pages) {
-  printer_->SetPrintedPagesCount(cookie, number_pages);
-}
-
 void PrintMockRenderThread::OnDidPrintDocument(
     const printing::mojom::DidPrintDocumentParams& params,
     IPC::Message* reply_msg) {

components/printing/test/print_mock_render_thread.h

@@ -76,7 +76,6 @@ class PrintMockRenderThread : public content::MockRenderThread {
   void OnScriptedPrint(const PrintHostMsg_ScriptedPrint_Params& params,
                        PrintMsg_PrintPages_Params* settings);
 
-  void OnDidGetPrintedPagesCount(int cookie, int number_pages);
   void OnDidPrintDocument(const printing::mojom::DidPrintDocumentParams& params,
                           IPC::Message* reply_msg);
 #if BUILDFLAG(ENABLE_PRINT_PREVIEW)