PrintPreview: Preview generation should not block print button.

chrome/renderer/print_web_view_helper.cc

Index: chrome/renderer/print_web_view_helper.cc
diff --git a/chrome/renderer/print_web_view_helper.cc b/chrome/renderer/print_web_view_helper.cc
index ef8e5d51472dfcaa29e60762b68c52e372cd88bc..d587d4dd10b0ea0421f2968dd732e9e229dd731a 100644
--- a/chrome/renderer/print_web_view_helper.cc
+++ b/chrome/renderer/print_web_view_helper.cc
@@ -200,7 +200,7 @@ void PrintWebViewHelper::OnPrintForPrintPreview(
   // chrome/browser/resources/print_preview.js
   WebElement pdf_element = document.getElementById("pdf-viewer");
   if (pdf_element.isNull()) {
-    NOTREACHED();
+    DidFinishPrinting(FAIL_PRINT);
     return;
   }
 
@@ -361,7 +361,7 @@ void PrintWebViewHelper::DidFinishPrinting(PrintingResult result) {
         web_view->mainFrame(),
         l10n_util::GetStringUTF16(IDS_PRINT_SPOOL_FAILED_ERROR_TEXT));
 
-    if (notify_browser_of_print_failure_) {
+    if (notify_browser_of_print_failure_ && print_pages_params_.get()) {
       int cookie = print_pages_params_->params.document_cookie;
       Send(new PrintHostMsg_PrintingFailed(routing_id(), cookie));
     }