TaskScheduler: Dispatch to STA for COM usage in platform_util_win.

R=robliao@chromium.org
TBR=thakis@chromium.org

Change-Id: I7e4c530b89f6c21f0197b7b7db2ec3046b45732b
Reviewed-on: https://chromium-review.googlesource.com/581736
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488691}

chrome/browser/platform_util_win.cc

@@ -108,9 +108,10 @@ void OpenExternalOnWorkerThread(const GURL& url) {
 }  // namespace
 
 void ShowItemInFolder(Profile* profile, const base::FilePath& full_path) {
-  PostTaskWithTraits(FROM_HERE,
-                     {base::MayBlock(), base::TaskPriority::USER_BLOCKING},
-                     base::Bind(&ShowItemInFolderOnWorkerThread, full_path));
+  base::CreateCOMSTATaskRunnerWithTraits(
+      {base::MayBlock(), base::TaskPriority::USER_BLOCKING})
+      ->PostTask(FROM_HERE,
+                 base::Bind(&ShowItemInFolderOnWorkerThread, full_path));
 }
 
 namespace internal {
@@ -132,9 +133,9 @@ void PlatformOpenVerifiedItem(const base::FilePath& path, OpenItemType type) {
 void OpenExternal(Profile* profile, const GURL& url) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
-  PostTaskWithTraits(FROM_HERE,
-                     {base::MayBlock(), base::TaskPriority::USER_BLOCKING},
-                     base::Bind(&OpenExternalOnWorkerThread, url));
+  base::CreateCOMSTATaskRunnerWithTraits(
+      {base::MayBlock(), base::TaskPriority::USER_BLOCKING})
+      ->PostTask(FROM_HERE, base::Bind(&OpenExternalOnWorkerThread, url));
 }
 
 }  // namespace platform_util