fix($compile): render nested transclusion at the root of a template

[petebacondarwin]

Closes #8914
Closes #8925

[caitp]

Looks good now

[petebacondarwin]

Merged.

[vojtajina]

Try to remove the ng-transclude directive and the test will still pass (transclusion still gets linked and appended) - just because there is no child element. That is wrong.

[vojtajina]

@jeffbcross @petebacondarwin This fix is wrong and we should revert it.

It links the transclusion when there is no child element instead of when ng-transclude directive is present. See my comments in test/ng/compileSpec.js.

Fixing this issue is hard. In other cases (when ng-transclude is on some child element) we use that element as a container - we pass that element to children as a transclusion and then, ng-transclude will mutate this element, without worrying that some other transclusion moved (transcluded) the container element somewhere else. In this cases, there is no container to mutate.

At the time when we are creating the transclusion (unbound transclusion, during compilation) we don't have the information that there is ng-transclude present which will append some content (because ng-transclude is just an arbitrary directive that asks for $transclude and does append the content later, during linking).

This fix is basically treating the case "no children element" as "it has ng-transclude". I don't think that's correct.

[petebacondarwin]

Ok let's revert as it was an unusual corner case anyway. Sorry to break things