Reland "[Test Automation] Improvements to WebContents action handling"

This reverts commit 36d372aecd8e3c77939b75cfaa516de4039124d4.

Reason for revert: Found a bug in a lower-level library, also attempting to use a frequently-changed piece of UI as a target for a test of a test library. Changed to a more stable target and worked around the deficiency in the lower-level library (with TODO for a follow-up).

There is one test that runs the risk of flaking, but we want to use that to determine why and where the holes are in our test instrumentation infrastructure. As a result, it would be better to selectively disable the test and reopen the attached bug if the flake still occurs.

Thank you!

Bug: 1471043

Original change's description:
> Revert "[Test Automation] Improvements to WebContents action handling"
>
> This reverts commit b5f01de6d094d0e0c949f040c45f112d6317418f.
>
> Reason for revert: Newly added test InteractiveBrowserTestUiTest.WatchForNonTabWebContentsActivation is breaking linux-chromeos-chrome. Revert-first policy applies.
>
> Original change's description:
> > [Test Automation] Improvements to WebContents action handling
> >
> > Provides the following:
> >  - ActivateSurface() now works for instrumented WebContents
> >  - FocusWebContents() [new] simulates the user initiating an interaction
> >    with the instrumented WebContents, allowing it to e.g. receive
> >    accelerators
> >  - SendAccelerator now works correctly for instrumented WebContents
> >  - Some corner cases around browser windows that were not previously
> >    handled by WidgetFocusObserver are now handled
> >
> > Change-Id: Iabee7b3f4460baa340d7d211a2f84ce301b5fce9
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4753798
> > Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
> > Reviewed-by: Kuan Huang <kuanhuang@chromium.org>
> > Commit-Queue: Dana Fried <dfried@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1180551}
>
> Change-Id: Ia183d590d959956f2ade2f946443a19f8de8f510
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4755111
> Commit-Queue: Jason Lin <lxj@google.com>
> Reviewed-by: Jason Lin <lxj@google.com>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Owners-Override: Jason Lin <lxj@google.com>
> Cr-Commit-Position: refs/heads/main@{#1180633}

Change-Id: Ida0590b3774740586160cbfb2ef75b34ba966107
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4897997
Commit-Queue: Kuan Huang <kuanhuang@chromium.org>
Reviewed-by: Kuan Huang <kuanhuang@chromium.org>
Auto-Submit: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1204197}