Revert of Implement the basic testing infrastructure for FindRequestManager. (patchset #5 id:100001 of https://codereview.chromium.org/1891773002/ )

Reason for revert:
All three of the FindRequestManagerTests failed on Android: https://build.chromium.org/p/chromium.linux/builders/Android%20Tests/builds/25938

Original issue's description:
> Implement the basic testing infrastructure for FindRequestManager.
>
> This patch adds find_request_manager_browsertest.cc, along with a few find-in-page tests that can already be tested (though not yet with cross-process frames). There are also some new testing files and some small changes to FindRequestManager to facilitate testing.
>
> Design doc for multi-process find-in-page: https://docs.google.com/a/google.com/document/d/12S_6X2MWWLoyJslajcajL2ELU7zhodPxMOxa8Bg4Wg0/edit?usp=sharing
>
> BUG=457440

[email protected],[email protected]
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=457440

Review URL: https://codereview.chromium.org/1910073002

Cr-Commit-Position: refs/heads/master@{#388816}
5 files changed