Previously, PhaseOutput produced a single AssetNode whose value it
would update whenever the forwarded output changed. This worked well
for a while, but once Phase started caring about the AssetNode's
origin, it became problematic. PhaseOutput would change the origin,
but Phase would have no way of knowing this, and the AssetNode would
end up sorted into the wrong place (treated as a forwarded node when
it shouldn't be, or vice versa).
This CL fixes that issue by removing the possibility of modifying an
AssetNode's origin. PhaseOutput now just creates a new AssetNode
instead. This has the additional benefit of cleaning up some
duplicated code in Phase.
R=rnystrom@google.com
BUG=
Review URL: https://codereview.chromium.org//26413003
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@28386 260f80e4-7a28-3924-810f-c04153c831b5
nweiz@google.com
96e9dce1d4