Backport some tests in /ipc to SingleThreadTaskEnvironment

These tests were previously migrated from single-threaded MessageLoop to
a multi-threaded TaskEnvironment (then named ScopedTaskEnvironment) as
part of crbug.com/891670.

//base OWNERS decided in retrospect that it was better to keep a
single-threaded option for TaskEnvironment and introduced
SingleThreadTaskEnvironment. This CL retrofits that decision for
/ipc.

This CL is a no-op if it passes CQ.

This CL was uploaded by git cl split.

[email protected]

Bug: 891670
Change-Id: I410de34fd2b80faf6403ee60d3a81e9a0ac40a6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787059
Auto-Submit: Gabriel Charette <[email protected]>
Commit-Queue: John Abd-El-Malek <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Cr-Commit-Position: refs/heads/master@{#694970}
diff --git a/ipc/ipc_mojo_bootstrap_unittest.cc b/ipc/ipc_mojo_bootstrap_unittest.cc
index 63c0f83d..4508369 100644
--- a/ipc/ipc_mojo_bootstrap_unittest.cc
+++ b/ipc/ipc_mojo_bootstrap_unittest.cc
@@ -107,7 +107,7 @@
 };
 
 TEST_F(IPCMojoBootstrapTest, Connect) {
-  base::test::TaskEnvironment task_environment;
+  base::test::SingleThreadTaskEnvironment task_environment;
   Connection connection(
       IPC::MojoBootstrap::Create(
           helper_.StartChild("IPCMojoBootstrapTestClient"),
@@ -132,7 +132,7 @@
 MULTIPROCESS_TEST_MAIN_WITH_SETUP(
     IPCMojoBootstrapTestClientTestChildMain,
     ::mojo::core::test::MultiprocessTestHelper::ChildSetup) {
-  base::test::TaskEnvironment task_environment;
+  base::test::SingleThreadTaskEnvironment task_environment;
   Connection connection(
       IPC::MojoBootstrap::Create(
           std::move(mojo::core::test::MultiprocessTestHelper::primordial_pipe),
@@ -153,7 +153,7 @@
 }
 
 TEST_F(IPCMojoBootstrapTest, ReceiveEmptyMessage) {
-  base::test::TaskEnvironment task_environment;
+  base::test::SingleThreadTaskEnvironment task_environment;
   Connection connection(
       IPC::MojoBootstrap::Create(
           helper_.StartChild("IPCMojoBootstrapTestEmptyMessage"),
@@ -180,7 +180,7 @@
 MULTIPROCESS_TEST_MAIN_WITH_SETUP(
     IPCMojoBootstrapTestEmptyMessageTestChildMain,
     ::mojo::core::test::MultiprocessTestHelper::ChildSetup) {
-  base::test::TaskEnvironment task_environment;
+  base::test::SingleThreadTaskEnvironment task_environment;
   Connection connection(
       IPC::MojoBootstrap::Create(
           std::move(mojo::core::test::MultiprocessTestHelper::primordial_pipe),