ES6 modules can be reordered incorrectly

[dfreedm]

I have a project which seems to make Closure Compiler reorder ES6 modules improperly, breaking functionality.

A small reproduction of this issue can be found at https://github.com/azakus/closure-reorder-import

In this reproduction, I use rollup and the npm package for closure on the same entry point. Rollup will produce the expected output, while closure seems to reorder the modules and produce an incorrect output

@ChadKillingsworth

[justinfagnani]

/sub and cc @FredKSchott

[ChadKillingsworth]

Sorry - I've been ushering through a lot of other PRs lately. I'll try to look at this soon.

[ChadKillingsworth]

For reference, the module tree looks like:

entry
 ├ b/b.js
 |   └ b/c.js
 ├ b/a.js
 ├ important.js
 ├ a/b.js
 └ a/a.js

The expected inclusion (depth first traversal) should be:

1. b/c.js
2. b/b.js
3. b/a.js
4. important.js
5. a/b.js
6. a/a.js
7. entry

[ChadKillingsworth]

Closed by #2641