Code: void PrintViewManager::OnShowScriptedPrintPreview(content::RenderFrameHost* rfh,
                                                  bool source_is_modifiable) {
  DCHECK(print_preview_rfh_);
  if (rfh != print_preview_rfh_)
    return;

  PrintPreviewDialogController* dialog_controller =
      PrintPreviewDialogController::GetInstance();
  if (!dialog_controller) {
    PrintPreviewDone();
     return;
   }
 
   dialog_controller->PrintPreview(web_contents());
   PrintHostMsg_RequestPrintPreview_Params params;
   params.is_modifiable = source_is_modifiable;
  PrintPreviewUI::SetInitialParams(
      dialog_controller->GetPrintPreviewForContents(web_contents()), params);
}

Vulnerability Type: 
CWE ID: CWE-20
Summary: Inappropriate implementation in modal dialog handling in Blink in Google Chrome prior to 60.0.3112.78 for Mac, Windows, Linux, and Android allowed a remote attacker to prevent a full screen warning from being displayed via a crafted HTML page.
Commit Message: If JavaScript shows a dialog, cause the page to lose fullscreen.

BUG=670135, 550017, 726761, 728276

Review-Url: https://codereview.chromium.org/2906133004
Cr-Commit-Position: refs/heads/master@{#478884}