Use TaskScheduler instead of blocking pool in chrome_screenshot_grabber.cc.

chrome/browser/ui/ash/chrome_screenshot_grabber.cc

Index: chrome/browser/ui/ash/chrome_screenshot_grabber.cc
diff --git a/chrome/browser/ui/ash/chrome_screenshot_grabber.cc b/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
index 6fdb08ccd0eb1377cf6af322b31fe82ccbcbd1c8..4ec03eb8669347c993b0058d91e5df0a0b567be9 100644
--- a/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
+++ b/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
@@ -18,6 +18,7 @@
 #include "base/metrics/user_metrics.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ -72,8 +73,6 @@ void CopyScreenshotToClipboard(scoped_refptr<base::RefCountedString> png_data) {
 }
 
 void ReadFileAndCopyToClipboardLocal(const base::FilePath& screenshot_path) {
-  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
-
   scoped_refptr<base::RefCountedString> png_data(new base::RefCountedString());
   if (!base::ReadFileToString(screenshot_path, &(png_data->data()))) {
     LOG(ERROR) << "Failed to read the screenshot file: "
@@ -281,9 +280,12 @@ std::string GetScreenshotBaseFilename() {
 ChromeScreenshotGrabber::ChromeScreenshotGrabber()
     : screenshot_grabber_(new ui::ScreenshotGrabber(
           this,
-          content::BrowserThread::GetBlockingPool()
-              ->GetTaskRunnerWithShutdownBehavior(
-                  base::SequencedWorkerPool::SKIP_ON_SHUTDOWN))),
+          base::CreateTaskRunnerWithTraits(
+              base::TaskTraits()
+                  .MayBlock()
+                  .WithPriority(base::TaskPriority::BACKGROUND)

[James Cook, 2017/04/26 20:46:44]

I think this should be USER_VISIBLE. The user is waiting for the screenshot
notification to appear.

[fdoray, 2017/04/27 13:35:31]

Done.

+                  .WithShutdownBehavior(
+                      base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN)))),
       profile_for_test_(NULL) {
   screenshot_grabber_->AddObserver(this);
 }