[ES6 modules] ModuleTreeLinker::FetchDescendants should not assume urls isn't empty.
Before this CL, we assumed "urls" in ModuleTreeLinker::FetchDescendants() to be non-empty
if record.[[RequestedModules]] is not empty.
However, this isn't always the case, as the resolved url may be in the ancestor list.
This CL removes the DCHECK based on this assumption, and complete the algorithm in that case.
TEST=ModuleTreeLinkerTest.FetchDependencyOfCyclicGraph
BUG=594639
Review-Url: https://codereview.chromium.org/2852963002
Cr-Commit-Position: refs/heads/master@{#468554}
2 files changed
