cc: Fix property tree position updates when rebuilding is skipped

cc: Fix property tree position updates when rebuilding is skipped

The parent_offset currently stored at each transform tree node sometimes
depends on the transform between some other node (which happens to
correspond to node's owning layer's parent's transform node) and the node's
parent. When this transform changes and the transform tree isn't rebuilt,
the parent_offset becomes stale. This CL replaces parent_offset with
source_offset, which is the portion of parent_offset that doesn't depend on
a transform between tree nodes, and adds a source_node_id to each node
so that the transform between nodes (when needed) can be recomputed
when the transform tree is updated.

BUG=480589
Committed: https://crrev.com/f09db896fac58260590729fbba5f285ba06b7cd3
Cr-Commit-Position: refs/heads/master@{#326894}

[ajuma, 2015-04-24 20:41:03]

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

[Ian Vollick, 2015-04-24 21:27:49]

On 2015/04/24 20:41:53, ajuma wrote:

lgtm!

[ajuma, 2015-04-24 21:49:23]

The CQ bit was checked by ajuma@chromium.org

[commit-bot: I haz the power, 2015-04-24 21:50:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1106013002/20001

[commit-bot: I haz the power, 2015-04-24 21:55:41]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-24 21:56:50]

Patchset 2 (id:??) landed as
https://crrev.com/f09db896fac58260590729fbba5f285ba06b7cd3
Cr-Commit-Position: refs/heads/master@{#326894}