Fix compile errors in flow analysis and type promotion test cases.

Change-Id: I4c16ddfeec8598bb07b8c1e44e914424da7199aa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108263
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

pkg/analyzer/test/src/dart/resolution/flow_analysis_test.dart

@@ -433,6 +433,7 @@ void f() { // f
     await trackCode(r'''
 void f(bool b, int i) { // f
   return;
+  Object _;
   do {} while (b);
   for (;;) {}
   for (_ in []) {}
@@ -444,6 +445,7 @@ void f(bool b, int i) { // f
 ''');
     verify(
       unreachableStatements: [
+        'Object _',
         'do {}',
         'for (;;',
         'for (_',
@@ -489,6 +491,7 @@ void f() { // f
   test_forEach() async {
     await trackCode(r'''
 void f() {
+  Object _;
   for (_ in [0, 1, 2]) {
     1;
     return;

pkg/analyzer/test/src/dart/resolution/type_promotion_test.dart

@@ -261,6 +261,7 @@ void f(bool b, Object x) {
   test_forEach_outerIsType_loopAssigned() async {
     await resolveCode(r'''
 void f(Object x) {
+  Object v1;
   if (x is String) {
     for (var _ in (v1 = [0, 1, 2])) {
       x; // 1