Don't call Chrome::print() if there is a provisional DocumentLoader

In this case, the frame isn't done loading, and we may attempt to print something bogus.

BUG=339075
TEST=Manually, on a google presentation with --enable-print-preview

Review URL: https://codereview.chromium.org/196833005

git-svn-id: svn://svn.chromium.org/blink/trunk@169509 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/frame/DOMWindow.cpp

@@ -979,7 +979,7 @@ void DOMWindow::print()
     if (!host)
         return;
 
-    if (m_frame->loader().documentLoader()->isLoading()) {
+    if (m_frame->loader().provisionalDocumentLoader() || m_frame->loader().documentLoader()->isLoading()) {
         m_shouldPrintWhenFinishedLoading = true;
         return;
     }