Use ScopedTaskEnvironment instead of MessageLoop in /chromeos/dbus/audio

MessageLoop will go away, eventually.

ScopedTaskEnvironment will per default start a ThreadPool, which should
be fine in most of the cases. If you belive your test needs to make sure
that no ThreadPool runs let me know and I will update the patch.

BUG=891670
This CL was uploaded by git cl split.

R=hychao@chromium.org

Change-Id: Ibcbbd7fefada7528724dbd81910a6a987a724876
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649364
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#670012}

chromeos/dbus/audio/cras_audio_client_unittest.cc

@@ -10,8 +10,8 @@
 #include <vector>
 
 #include "base/bind.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "dbus/message.h"
 #include "dbus/mock_bus.h"
 #include "dbus/mock_object_proxy.h"
@@ -437,7 +437,7 @@ class CrasAudioClientTest : public testing::Test {
   // The interface name.
   const std::string interface_name_;
   // A message loop to emulate asynchronous behavior.
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   // The mock bus.
   scoped_refptr<dbus::MockBus> mock_bus_;
   // The mock object proxy.
@@ -476,7 +476,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     output_mute_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -490,7 +490,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     input_mute_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -504,7 +504,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     nodes_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -518,7 +518,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     active_output_node_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -532,7 +532,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     active_input_node_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -546,7 +546,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     output_node_volume_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -560,7 +560,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     hotword_triggered_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -574,7 +574,7 @@ class CrasAudioClientTest : public testing::Test {
       dbus::ObjectProxy::OnConnectedCallback* on_connected_callback) {
     number_of_active_streams_changed_handler_ = signal_callback;
     const bool success = true;
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*on_connected_callback),
                                   interface_name, signal_name, success));
   }
@@ -588,7 +588,7 @@ class CrasAudioClientTest : public testing::Test {
     EXPECT_EQ(expected_method_name_, method_call->GetMember());
     dbus::MessageReader reader(method_call);
     argument_checker_.Run(&reader);
-    message_loop_.task_runner()->PostTask(
+    scoped_task_environment_.GetMainThreadTaskRunner()->PostTask(
         FROM_HERE, base::BindOnce(std::move(*response), response_));
   }