chromeos: Eliminate ash::Config::MASH_DEPRECATED

We haven't run ash in this mode for months, since the switch to ws2 /
window-service-as-a-library.

* CursorManager exists in ws2, so always use it
* Docked magnifier works in SingleProcessMash, and will need to be
  fixed separately for multi-process
* Eliminate unused DragWindowResizerMash. Window dragging across
  displays works for both single-process and multi-process mash
* Always use EventTargetingPolicy::TARGET_AND_DESCENDENTS in exo.
  Manually verified that clicks go to the right place in both
  single-process and multi-process mash.
* Remove many unused includes

I had to disable one ash_unittest for NonClientFrameController.

[email protected]

Bug: 631103, 637853, 646565, 705592, 756163, 839521
Test: ash_unittests
Change-Id: Iab64339029a33921274089ca4cb57a8f037f6f88
Reviewed-on: https://chromium-review.googlesource.com/1200483
Commit-Queue: James Cook <[email protected]>
Reviewed-by: Xiyuan Xia <[email protected]>
Reviewed-by: Mitsuru Oshima <[email protected]>
Cr-Commit-Position: refs/heads/master@{#588626}
76 files changed