Timeline: add reference to root node of layer in Rasterize event

- change node id type to long long for consistency;
- keep map of layer ids to node id, update it during Paint;
- add root node id of rasterized layer in Rasterize event;
- generalize related node handling in TimelinePresentationModel.

R=vsevik@chromium.org

Review URL: https://codereview.chromium.org/14741014

git-svn-id: svn://svn.chromium.org/blink/trunk@150572 bbb929c8-8fbe-4397-9dbb-9b2b20218538
9 files changed