Backport some tests in /components/spellcheck 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
/components/spellcheck.

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

This CL was uploaded by git cl split.

R=groby@chromium.org

Bug: 891670
Change-Id: I49d8195a5ecb42ceacf78c3721550747cd501486
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786946
Auto-Submit: Gabriel Charette <gab@chromium.org>
Commit-Queue: Rachel Blum <groby@chromium.org>
Reviewed-by: Rachel Blum <groby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695752}

components/spellcheck/browser/spellcheck_host_metrics_unittest.cc

@@ -27,7 +27,7 @@ class SpellcheckHostMetricsTest : public testing::Test {
   void RecordWordCountsForTesting() { metrics_->RecordWordCounts(); }
 
  private:
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
   std::unique_ptr<SpellCheckHostMetrics> metrics_;
 };
 

components/spellcheck/browser/spellcheck_platform_mac_unittest.cc

@@ -49,8 +49,8 @@ class SpellcheckPlatformMacTest: public testing::Test {
                                   base::Unretained(this)));
   }
 
-  base::test::TaskEnvironment task_environment_{
-      base::test::TaskEnvironment::MainThreadType::UI};
+  base::test::SingleThreadTaskEnvironment task_environment_{
+      base::test::SingleThreadTaskEnvironment::MainThreadType::UI};
   spellcheck_platform::ScopedEnglishLanguageForTest scoped_language_;
 };
 

components/spellcheck/renderer/spellcheck_unittest.cc

@@ -130,7 +130,7 @@ class SpellCheckTest : public testing::Test {
  private:
   spellcheck::EmptyLocalInterfaceProvider embedder_provider_;
   std::unique_ptr<SpellCheck> spell_check_;
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
 };
 
 struct MockTextCheckingResult {