GitLab

Now that FindinPageController's completionBlocks don't get executed,
use a TestFindInPageResponseDelegate. Also removes detachFromWebState
call because it actually breaks things by nulling out the webstate before
it is destroyed.

Bug: 919685, 996324
Change-Id: I503c9452d5ee9120aec0c9c1b79fd91379996965
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1749306Reviewed-by: Yi Su <mrsuyi@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691660}