Automation API: Get rid of host node and get parent from C++ bindings instead

Automation API: Get rid of host node and get parent from C++ bindings instead

This is just a refactoring, it's slightly less fragile to have all of the
code to walk "up" trees in one place rather than in both C++ and in JS
automation bindings.

BUG=none

[dmazzoni, 2017-03-23 23:11:32]

dmazzoni@chromium.org changed reviewers:
+ dtseng@chromium.org

[David Tseng, 2017-03-24 21:38:12]

Please try to retain the idea behind the js bindings when converting into
native. i.e. you should probably do the caching of the parent -> host
relationship somewhere in OnNodeDataWillChange and don't do the expensive
lookup. I'm a little concerned because the native GetParent codepath wasn't ever
hit.

[David Tseng, 2017-03-24 21:40:48]

Automation API: Get rid of host node and get parent from C++ bindings instead

Please rephrase; there's a 'and use' probably left out or something.

[David Tseng, 2017-03-24 21:43:15]

The CQ bit was checked by dtseng@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-24 21:43:41]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-24 22:44:47]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-03-24 22:44:48]

Dry run: Try jobs failed on following builders:
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)