Use async/await in all analysis domain tests.

pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart

Index: pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart
diff --git a/pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart b/pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart
index 13c50736daa011b623f15715c908c47d594f678b..0ce9e1642d04b80e6442ea2db42dd6d1ad0cacc7 100644
--- a/pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart
+++ b/pkg/analysis_server/test/analysis/notification_analyzedFiles_test.dart
@@ -49,24 +49,21 @@ class AnalysisNotificationAnalyzedFilesTest extends AbstractAnalysisTest {
     createProject();
   }
 
-  test_afterAnalysis() {
+  test_afterAnalysis() async {
     addTestFile('''
 class A {}
 ''');
-    return waitForTasksFinished().then((_) {
-      return prepareAnalyzedFiles().then((_) {
-        assertHasFile(testFile);
-      });
-    });
+    await waitForTasksFinished();
+    await prepareAnalyzedFiles();
+    assertHasFile(testFile);
   }
 
-  test_beforeAnalysis() {
+  test_beforeAnalysis() async {
     addTestFile('''
 class A {}
 ''');
-    return prepareAnalyzedFiles().then((_) {
-      assertHasFile(testFile);
-    });
+    await prepareAnalyzedFiles();
+    assertHasFile(testFile);
   }
 
   test_insignificant_change() async {