Fix bad type-inferrence for logical expressions.

tests/compiler/dart2js/simple_inferrer_and_or_test.dart

Index: tests/compiler/dart2js/simple_inferrer_and_or_test.dart
diff --git a/tests/compiler/dart2js/simple_inferrer_and_or_test.dart b/tests/compiler/dart2js/simple_inferrer_and_or_test.dart
index 97531a6846a85da489047542b61f7fc5d85a6667..832edd5fd020e4ce178f9bc104f5560780c7350b 100644
--- a/tests/compiler/dart2js/simple_inferrer_and_or_test.dart
+++ b/tests/compiler/dart2js/simple_inferrer_and_or_test.dart
@@ -45,6 +45,15 @@ returnDyn6() {
   return a;
 }
 
+returnDyn7b(x) => x;
+
+returnDyn7() {
+  var a = "foo";
+  if (a.length == 3) a = 52;
+  if ((a is int) || (a is String && true)) returnDyn7b(a);
+  return a;
+}
+
 main() {
   returnDyn1();
   returnDyn2();
@@ -52,6 +61,7 @@ main() {
   returnDyn4();
   returnDyn5();
   returnDyn6();
+  returnDyn7();
 }
 """;
 
@@ -77,5 +87,7 @@ void main() {
     checkReturn('returnDyn4', compiler.typesTask.dynamicType.nonNullable());
     checkReturn('returnDyn5', compiler.typesTask.dynamicType.nonNullable());
     checkReturn('returnDyn6', compiler.typesTask.dynamicType.nonNullable());
+    checkReturn('returnDyn7', subclassOfInterceptor);
+    checkReturn('returnDyn7b', subclassOfInterceptor);
   }));
 }