Revert of Fix crash after Launcher drag/drop (take 2) (patchset #1 id:1 of https...

Revert of Fix crash after Launcher drag/drop (take 2) (patchset #1 id:1 of https://codereview.chromium.org/792883006/)

Reason for revert:
The new test is still causing problems. See http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20%28valgrind%29%282%29/builds/44030.

The test appears to be flaky. It has failed on that bot on 4 of the 6 runs since this change landed.

BTW I'd add calamity@ to any reviews of dragging in the launcher as he has fixed many bugs there and is aware of many subtleties in the code.

Original issue's description:
> Fix crash after Launcher drag/drop (take 2)
>
> BUG=439055
> TEST=In Launcher, drag app to solitary folder on second page
>
> This is a retry of https://codereview.chromium.org/780023002/ ,
> which was reverted after commit due to a failed valgrind test.
>
> Committed: https://crrev.com/62e30ca368387d4edbbbf5c721f30881586b2387
> Cr-Commit-Position: refs/heads/master@{#309235}

TBR=jennyz@chromium.org,glevin@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=439055

Review URL: https://codereview.chromium.org/820943003

Cr-Commit-Position: refs/heads/master@{#309386}