Use ScopedTaskEnvironment instead of MessageLoopForUI in ios tests.

ScopedTaskEnvironment allows usage of ThreadTaskRunnerHandle and
base/task_scheduler/post_task.h within its scope. It should be
instantiated in everytest that uses either of these APIs
(i.e. no test should instantiate a MessageLoop directly).

Motivation for ScopedTaskEnvironment can be found in:
https://docs.google.com/document/d/1QabRo8c7D9LsYY3cEcaPQbOCLo8Tu-6VLykYXyl3Pkk/edit

BUG=708584
R=gab@chromium.org
TBR=marq@chromium.org

Review-Url: https://codereview.chromium.org/2846073002
Cr-Commit-Position: refs/heads/master@{#467968}

ios/chrome/browser/ui/settings/time_range_selector_collection_view_controller_unittest.mm

@@ -5,7 +5,7 @@
 #import "ios/chrome/browser/ui/settings/time_range_selector_collection_view_controller.h"
 
 #include "base/files/file_path.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/browsing_data/core/pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
@@ -32,6 +32,10 @@ const NSInteger kNumberOfItems = 5;
 class TimeRangeSelectorCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
+  TimeRangeSelectorCollectionViewControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
@@ -64,7 +68,7 @@ class TimeRangeSelectorCollectionViewControllerTest
     EXPECT_EQ(accessory_type, cell.accessoryType);
   }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   std::unique_ptr<PrefService> pref_service_;
   id delegate_;
   TimeRangeSelectorCollectionViewController* time_range_selector_controller_;

ios/chrome/browser/ui/settings/translate_collection_view_controller_unittest.mm

@@ -8,7 +8,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_member.h"
@@ -42,6 +42,10 @@ const char kLanguage2[] = "pirate";
 class TranslateCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
+  TranslateCollectionViewControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
@@ -66,7 +70,7 @@ class TranslateCollectionViewControllerTest
     return factory.Create(registry.get());
   }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   std::unique_ptr<PrefService> pref_service_;
 };
 

ios/chrome/browser/ui/settings/voicesearch_collection_view_controller_unittest.mm

@@ -9,7 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/mac/foundation_util.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/prefs/pref_member.h"
 #include "components/prefs/pref_registry_simple.h"
@@ -33,6 +33,10 @@ namespace {
 class VoicesearchCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
+  VoicesearchCollectionViewControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
@@ -58,7 +62,7 @@ class VoicesearchCollectionViewControllerTest
                                                        inSection:0]]);
   }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   std::unique_ptr<PrefService> pref_service_;
 };
 

ios/web/webui/url_fetcher_block_adapter_unittest.mm

@@ -10,6 +10,7 @@
 #include "base/files/file_util.h"
 #include "base/run_loop.h"
 #include "base/strings/sys_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "net/url_request/url_request_status.h"
 #include "net/url_request/url_request_test_util.h"
@@ -22,8 +23,12 @@ namespace web {
 // Test fixture for URLFetcherBlockAdapter.
 class URLFetcherBlockAdapterTest : public PlatformTest {
  protected:
+  URLFetcherBlockAdapterTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   // Required for base::MessageLoop::current().
-  base::MessageLoopForUI loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 // Tests that URLFetcherBlockAdapter calls its completion handler with the