[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in metrics

MessageLoop will go away, eventually.

BUG=891670

Change-Id: Ic4527ecbd1e1485a57fe5210db485a839d29f894
Reviewed-on: https://chromium-review.googlesource.com/c/1352757Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#612126}

components/metrics/child_call_stack_profile_collector_unittest.cc

@@ -9,8 +9,8 @@
 #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 "mojo/public/cpp/bindings/binding.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/metrics_proto/sampled_profile.pb.h"
@@ -50,7 +50,7 @@ class ChildCallStackProfileCollectorTest : public testing::Test {
     return child_collector_.profiles_;
   }
 
-  base::MessageLoop loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   mojom::CallStackProfileCollectorPtr receiver_;
   std::unique_ptr<Receiver> receiver_impl_;
   ChildCallStackProfileCollector child_collector_;

components/metrics/single_sample_metrics_factory_impl_unittest.cc

@@ -4,11 +4,11 @@
 
 #include "components/metrics/single_sample_metrics_factory_impl.h"
 
-#include "base/message_loop/message_loop.h"
 #include "base/metrics/dummy_histogram.h"
 #include "base/run_loop.h"
 #include "base/test/gtest_util.h"
 #include "base/test/metrics/histogram_tester.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread.h"
 #include "components/metrics/single_sample_metrics.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -74,7 +74,7 @@ class SingleSampleMetricsFactoryImplTest : public testing::Test {
                                                  kBucketCount);
   }
 
-  base::MessageLoop message_looqp_;
+  base::test::ScopedTaskEnvironment task_environment_;
   SingleSampleMetricsFactoryImpl* factory_;
   base::Thread thread_;
   size_t provider_count_ = 0;