This does two things:

1) When the it returns from the Print Dialog it checks to see if the
PD_PRINTTOFILE flags is set then then set the the info into the PrintSettings
2) IF we are printing to a file, but not a file driver, then check to see if
the file name is the special "FILE:" (as per the MS documentation)
Bug 170332 r=dcone sr=alecf

embedding/components/printingui/src/win/nsPrintDialogUtil.cpp

@@ -976,6 +976,25 @@ ShowNativePrintDialog(HWND              aHWnd,
       char* device = &(((char *)devnames)[devnames->wDeviceOffset]);
       char* driver = &(((char *)devnames)[devnames->wDriverOffset]);
 
+      // Check to see if the "Print To File" control is checked
+      // then take the name from devNames and set it in the PrintSettings
+      //
+      // NOTE:
+      // As per Microsoft SDK documentation the returned value offset from
+      // devnames->wOutputOffset is either "FILE:" or NULL
+      // if the "Print To File" checkbox is checked it MUST be "FILE:"
+      // We assert as an extra safety check.
+      if (prntdlg.Flags & PD_PRINTTOFILE) {
+        char* fileName = &(((char *)devnames)[devnames->wOutputOffset]);
+        NS_ASSERTION(strcmp(fileName, "FILE:") == 0, "FileName must be `FILE:`");
+        aPrintSettings->SetToFileName(NS_ConvertASCIItoUCS2(fileName).get());
+        aPrintSettings->SetPrintToFile(PR_TRUE);
+      } else {
+        // clear "print to file" info
+        aPrintSettings->SetPrintToFile(PR_FALSE);
+        aPrintSettings->SetToFileName(nsnull);
+      }
+
       nsCOMPtr<nsIPrintSettingsWin> psWin(do_QueryInterface(aPrintSettings));
       // Setup local Data members
       psWin->SetDeviceName(device);
@@ -1294,6 +1313,25 @@ ShowNativePrintDialogEx(HWND              aHWnd,
       char* device = &(((char *)devnames)[devnames->wDeviceOffset]);
       char* driver = &(((char *)devnames)[devnames->wDriverOffset]);
 
+      // Check to see if the "Print To File" control is checked
+      // then take the name from devNames and set it in the PrintSettings
+      //
+      // NOTE:
+      // As per Microsoft SDK documentation the returned value offset from
+      // devnames->wOutputOffset is either "FILE:" or NULL
+      // if the "Print To File" checkbox is checked it MUST be "FILE:"
+      // We assert as an extra safety check.
+      if (prntdlg.Flags & PD_PRINTTOFILE) {
+        char* fileName = &(((char *)devnames)[devnames->wOutputOffset]);
+        NS_ASSERTION(strcmp(fileName, "FILE:") == 0, "FileName must be `FILE:`");
+        aPrintSettings->SetToFileName(NS_ConvertASCIItoUCS2(fileName).get());
+        aPrintSettings->SetPrintToFile(PR_TRUE);
+      } else {
+        // clear "print to file" info
+        aPrintSettings->SetPrintToFile(PR_FALSE);
+        aPrintSettings->SetToFileName(nsnull);
+      }
+
       nsCOMPtr<nsIPrintSettingsWin> psWin(do_QueryInterface(aPrintSettings));
       // Setup local Data members
       psWin->SetDeviceName(device);

gfx/src/windows/nsDeviceContextSpecWin.cpp

@@ -372,6 +372,21 @@ CheckForPrintToFile(nsIPrintSettings* aPS, LPTSTR aPrinterName, PRUnichar* aUPri
     CheckForPrintToFileWithName((char*)NS_ConvertUCS2toUTF8(aUPrinterName).get(), toFile);
   }
 #endif
+  // Since the driver wasn't a "Print To File" Driver, check to see
+  // if the name of the file has been set to the special "FILE:"
+  if (!toFile) {
+    nsXPIDLString toFileName;
+    aPS->GetToFileName(getter_Copies(toFileName));
+    if (toFileName) {
+      if (*toFileName) {
+        if (toFileName.Equals(NS_LITERAL_STRING("FILE:"))) {
+          // this skips the setting of the "print to file" info below
+          // which we don't want to do.
+          return NS_OK; 
+        }
+      }
+    }
+  }
   aPS->SetPrintToFile(toFile);
   if (toFile) {
     rv = GetFileNameForPrintSettings(aPS);