Bug 793473, propagate mDontPrint to descendants, r=roc

layout/printing/nsPrintEngine.cpp

@@ -1843,7 +1843,7 @@ nsPrintEngine::ReflowDocList(nsPrintObject* aPO, bool aSetPixelScale)
   if (aPO->mParent && aPO->mParent->mPresShell) {
     nsIFrame* frame = aPO->mContent ? aPO->mContent->GetPrimaryFrame() : nullptr;
     if (!frame || !frame->GetStyleVisibility()->IsVisible()) {
-      aPO->mDontPrint = true;
+      SetPrintPO(aPO, false);
       aPO->mInvisible = true;
       return NS_OK;
     }