AU: when cutting a cycle, add proper dependencies.

AU: when cutting a cycle, add proper dependencies.

The old behavior was:

Imagine a cycle: A->B->C->D->A. We cut A->B which creates the graph:
B->C->D->A->New. We depended on B to depend (indirectly) on New.

The problem is, say we cut two edges, A->B and C->D. Then the result
would be: D->A->New and B->C->New2. Now, B no longer depdends
(directly or indirectly) on New.

Now, When we cut a cycle, we have both the src/dst of the cut edge
depends on the New node. Following the example, this new behavior
gives us:
A->New<-B->C->New2<-D->A

It's both cycle free and doesn't lose the fact that B depends New.

BUG=chromium-os:5061
TEST=unittest, tested on generating delta that needed this fix

[petkov, 2010-07-23 06:39:09]

LGTM