Combine clips in content target space.

Combine clips in content target space.

We currently combine clips in the target space of the clip's transform
node. This is incorrect. We want to combine clips in the space of the
transform node's _content_ target space.

BUG=386810
Committed: https://crrev.com/67394b4da49066bdea3d1dfea69e063a9060920d
Cr-Commit-Position: refs/heads/master@{#319789}

[Ian Vollick, 2015-03-09 20:44:31]

vollick@chromium.org changed reviewers:
+ enne@chromium.org

[enne (OOO), 2015-03-09 21:44:19]

lgtm

I think I have some quibbles about content_target_id vs target_id now that I
understand better how they're working.  I think target_id is just
content_target_id's parent and so can be removed, but that's sort of orthogonal
to this.

[Ian Vollick, 2015-03-09 22:32:34]

The CQ bit was checked by vollick@chromium.org

[commit-bot: I haz the power, 2015-03-09 22:33:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/991013002/1

[commit-bot: I haz the power, 2015-03-10 00:22:43]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-10 00:23:48]

Patchset 1 (id:??) landed as
https://crrev.com/67394b4da49066bdea3d1dfea69e063a9060920d
Cr-Commit-Position: refs/heads/master@{#319789}