Implement inference tests for logical operators.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
index a9047a149e07fc01e3416c6b091bf396fc01e061..aab7e7a964fccf8b38ef2b44aba26153d82eeea2 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -1074,8 +1074,14 @@ class KernelLogicalExpression extends LogicalExpression
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
-    // TODO(scheglov): implement.
-    return typeNeeded ? const DynamicType() : null;
+    typeNeeded = inferrer.listener.logicalExpressionEnter(this, typeContext) ||
+        typeNeeded;
+    var boolType = inferrer.coreTypes.boolClass.rawType;
+    inferrer.inferExpression(left, boolType, false);
+    inferrer.inferExpression(right, boolType, false);
+    var inferredType = typeNeeded ? boolType : null;
+    inferrer.listener.logicalExpressionExit(this, inferredType);
+    return inferredType;
   }
 }