Reland of land: mus: Add views_mus_interactive_ui_tests target (patchset #1 id:1 of https://codereview.chromium.org/1984403002/ )

Reason for revert:
Relanding (this doesn't appear to have caused the compile failure on Win)

Original issue's description:
> Revert of Reland: mus: Add views_mus_interactive_ui_tests target (patchset #2 id:20001 of https://codereview.chromium.org/1982963002/ )
>
> Reason for revert:
> Speculative revert for compile failure on Win: https://uberchromegw.corp.google.com/i/chromium/builders/Win/builds/43482
>
> Original issue's description:
> > Reland: mus: Add views_mus_interactive_ui_tests target
> >
> > Previous attempt had a size_t to int warning on Windows, which was suppressed in chrome's interactive_ui_tests but not this new target. See https://codereview.chromium.org/1972363002/
> >
> > * Run widget_interactive_uitests.cc in the new target.
> > * Added a shared "test_support" target in ui/views/mus.
> > * Pull ViewsMusTestSuite into its own file so I can share it.
> > * Also make ViewsTestBase::IsMus static so I can call it before the
> >   PlatformTestHelper is initialized.
> > * Disable a bunch of tests that fail on mus (I filed bugs for them).
> > * Fix an unnecessary size_t to int conversion
> >
> > BUG=602036
> > TEST=views_mus_interactive_ui_tests on mus, interactive_ui_tests elsewhere
> > [email protected], [email protected], [email protected]
> >
> > Committed: https://crrev.com/ba13ca8e09763be3d4a93ef3d2d495aa806ddd77
> > Cr-Commit-Position: refs/heads/master@{#394153}
>
> [email protected]
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=602036
>
> Committed: https://crrev.com/78edbe6407945f0e2c8d1c7dfc873e398150ad45
> Cr-Commit-Position: refs/heads/master@{#394158}

[email protected]
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=602036

Review-Url: https://codereview.chromium.org/1990453003
Cr-Commit-Position: refs/heads/master@{#394161}
21 files changed