No issue - Fix some fatal printing assertions.

- Turn a fatal assert into a warning if we can't guarantee a drawTarget.
  This should not be fatal since the DrawTarget is checked later.
- Remove a fatal assertion if a display table background is cross-document
  since non-display iframes may cause this situation without it being an
  error.

gfx/thebes/PrintTarget.cpp

@@ -58,7 +58,7 @@ PrintTarget::MakeDrawTarget(const IntSize& aSize,
 
   // This should not be called outside of BeginPage()/EndPage() calls since
   // some backends can only provide a valid DrawTarget at that time.
-  MOZ_ASSERT(mHasActivePage, "We can't guarantee a valid DrawTarget");
+  NS_WARNING_ASSERTION(mHasActivePage, "We can't guarantee a valid DrawTarget without an active page. Content may be missing.");
 
   if (cairo_surface_status(mCairoSurface)) {
     return nullptr;

layout/tables/nsTableFrame.h

@@ -81,9 +81,6 @@ class nsDisplayTableBackgroundSet {
   nsDisplayTableBackgroundSet(nsDisplayListBuilder* aBuilder, nsIFrame* aTable)
       : mBuilder(aBuilder) {
     mPrevTableBackgroundSet = mBuilder->SetTableBackgroundSet(this);
-    mozilla::DebugOnly<const nsIFrame*> reference =
-        mBuilder->FindReferenceFrameFor(aTable, &mToReferenceFrame);
-    MOZ_ASSERT(nsLayoutUtils::IsAncestorFrameCrossDoc(reference, aTable));
     mDirtyRect = mBuilder->GetDirtyRect();
   }