Move the DownloadTargetDeterminer Adobe Reader Check to use the COM STA Task Runner

BUG=706512

Change-Id: Ib252b2e692f36494e829eeefdb9664fb82f34909
Reviewed-on: https://chromium-review.googlesource.com/576309Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487589}

chrome/browser/download/download_target_determiner.cc

@@ -11,6 +11,7 @@
 #include "base/rand_util.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
+#include "base/task_runner_util.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
@@ -559,8 +560,11 @@ DownloadTargetDeterminer::Result
     return CONTINUE;
   }
 
-  base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, {base::MayBlock()}, base::Bind(&::IsAdobeReaderUpToDate),
+  // IsAdobeReaderUpToDate() needs to be run with COM as it makes COM calls via
+  // AssocQueryString() in IsAdobeReaderDefaultPDFViewer().
+  base::PostTaskAndReplyWithResult(
+      base::CreateCOMSTATaskRunnerWithTraits({base::MayBlock()}).get(),
+      FROM_HERE, base::Bind(&::IsAdobeReaderUpToDate),
       base::Bind(&DownloadTargetDeterminer::DetermineIfAdobeReaderUpToDateDone,
                  weak_ptr_factory_.GetWeakPtr()));
   return QUIT_DOLOOP;