Remove MessageLoopForIO references

Remove references in /device/bluetooth/bluez

MessageLoopForIO is going away soon. Use SingleThreadTaskExecutor for
main functions and SingleThreadTaskEnvironment for tests instead. Both
are no op changes.

This CL was uploaded by git cl split.

R=mcchou@chromium.org

Bug: 891670
Change-Id: I4b67ceda2cf508e5f5d76493c5d2aa05e3619924
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1780738
Auto-Submit: Carlos Caballero <carlscab@google.com>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699662}

device/bluetooth/bluez/bluetooth_advertisement_bluez_unittest.cc

@@ -12,8 +12,8 @@
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/task_environment.h"
 #include "device/bluetooth/bluetooth_adapter.h"
 #include "device/bluetooth/bluetooth_adapter_factory.h"
 #include "device/bluetooth/bluetooth_advertisement.h"
@@ -166,7 +166,8 @@ class BluetoothAdvertisementBlueZTest : public testing::Test {
 
   BluetoothAdvertisement::ErrorCode last_error_code_;
 
-  base::MessageLoopForIO message_loop_;
+  base::test::SingleThreadTaskEnvironment task_environment_{
+      base::test::SingleThreadTaskEnvironment::MainThreadType::IO};
 
   std::unique_ptr<TestBluetoothAdvertisementObserver> observer_;
   scoped_refptr<BluetoothAdapter> adapter_;