Code: void AcceleratedStaticBitmapImage::CheckThread() {
  if (detach_thread_at_next_check_) {
    thread_checker_.DetachFromThread();
    detach_thread_at_next_check_ = false;
  }
  CHECK(thread_checker_.CalledOnValidThread());
}

Vulnerability Type: Overflow 
CWE ID: CWE-119
Summary: Incorrect, thread-unsafe use of SkImage in Canvas in Google Chrome prior to 71.0.3578.80 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
Commit Message: Fix *StaticBitmapImage ThreadChecker and unaccelerated SkImage destroy

- AcceleratedStaticBitmapImage was misusing ThreadChecker by having its
own detach logic. Using proper DetachThread is simpler, cleaner and
correct.
- UnacceleratedStaticBitmapImage didn't destroy the SkImage in the
proper thread, leading to GrContext/SkSp problems.

Bug: 890576
Change-Id: Ic71e7f7322b0b851774628247aa5256664bc0723
Reviewed-on: https://chromium-review.googlesource.com/c/1307775
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604427}