Get print preview intitiator before ClearInitiatorDetails().

BUG=407080

Review URL: https://codereview.chromium.org/473683005

Cr-Commit-Position: refs/heads/master@{#291836}

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

@@ -834,6 +834,7 @@ void PrintPreviewHandler::HandlePrint(const base::ListValue* args) {
 
     // Do this so the initiator can open a new print preview dialog, while the
     // current print preview dialog is still handling its print job.
+    WebContents* initiator = GetInitiator();
     ClearInitiatorDetails();
 
     // The PDF being printed contains only the pages that the user selected,
@@ -853,7 +854,6 @@ void PrintPreviewHandler::HandlePrint(const base::ListValue* args) {
     // printing has finished. Then the dialog closes and PrintPreviewDone() gets
     // called. In the case below, since the preview dialog will be hidden and
     // not closed, we need to make this call.
-    WebContents* initiator = GetInitiator();
     if (initiator) {
       printing::PrintViewManager* print_view_manager =
           printing::PrintViewManager::FromWebContents(initiator);