Revert of Have CanvasAsyncBlobCreator's delayed task keep a weak |this| also. (patchset #1 id:1 of https://codereview.chromium.org/2069533002/ )

Reason for revert:
This CL makes blink_perf.canvas fail on perf bots. See the bug for details.

BUG=620043

Original issue's description:
> Have CanvasAsyncBlobCreator's delayed task keep a weak |this| also.
>
> Followup r399445 and dually have the delayed task that's
> posted to check if the idle task has gone ahead, also keep
> a weak |this| reference. The non-winning CanvasAsyncBlobCreator
> posted main thread tasks can safely be cancelled & dropped if
> a GC happens to go ahead.
>
> R=
> BUG=
>
> Committed: https://crrev.com/c0db5076c1c2b626aec53e2c8023b79e27820959
> Cr-Commit-Position: refs/heads/master@{#399675}

TBR=haraken@chromium.org,sigbjornf@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review-Url: https://codereview.chromium.org/2062243003
Cr-Commit-Position: refs/heads/master@{#399775}
1 file changed