Revert of Support modal windows (patchset #4 id:80001 of https://codereview.chromium.org/662763002/)

Reason for revert:
Reverting because this CL because WithOrWithoutTargeter.* introduced a memory leak and made all of the Athena Asan tests fail http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20(1)

Based on tools/lsan/suppressions.txt reverting is now preferred over adding a suppression

Original issue's description:
> Support modal windows
>
> * New ContainerParams
>  -  default_parent to specify the default parent when no
>     transient parent is specified.
>  - modal_container_priority now controls the modal container
>    used for a modal window created for the given container.
>  - if not specified, it will fallback downwards to find one.
>  - if window is specified as always_on_top, it will use top
>    most modal container.
>
> * Changed network selector/shutdown dialog to use the new API.
>
> * Other change:
>  Separated test windows to athena/test/base/test_windows.h
>
> BUG=410499
> TBR=sky@chromium.org,reed@chromium.org
> TEST=coverd by unit tests
>
> Committed: https://crrev.com/4903fd36b2b36f00efeb1b7bba81b7de6e9457a3
> Cr-Commit-Position: refs/heads/master@{#300192}

TBR=mukai@chromium.org,sky@chromium.org,reed@chromium.org,oshima@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=410499

Review URL: https://codereview.chromium.org/665803003

Cr-Commit-Position: refs/heads/master@{#300226}
31 files changed