The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1966e9f24298b0a2183a362412c09d39f5d19c03

commit 1966e9f24298b0a2183a362412c09d39f5d19c03
Author: James Cook <jamescook@chromium.org>
Date: Wed Jul 05 02:36:26 2017

chromeos: Migrate ChromeScreenshotGrabber to TaskScheduler

Use the same sequenced task runner for ChromeScreenshotGrabber and
ui::ScreenshotGrabber to ensure that multiple screenshots taken
rapidly are processed in the same order.

Bug:  667892 ,  737162 
Test: manually take screenshots with Ctrl-F5, check disk and clipboard
Change-Id: I48f557adb6dc9f7b63ab90c852947f6505e344de
Reviewed-on: https://chromium-review.googlesource.com/549970
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484181}
[modify] https://crrev.com/1966e9f24298b0a2183a362412c09d39f5d19c03/chrome/browser/ui/ash/chrome_screenshot_grabber.cc