Use "bool" as the downward inference context for assert conditions.

pkg/front_end/testcases/inference/assert_initializer.dart

Index: pkg/front_end/testcases/inference/assert_initializer.dart
diff --git a/pkg/front_end/testcases/inference/assert_initializer.dart b/pkg/front_end/testcases/inference/assert_initializer.dart
index 3a4ec19f024042b13e1d432936a8dc8eb45a457a..8f06330f2f372f173f234ade0fe502227e186701 100644
--- a/pkg/front_end/testcases/inference/assert_initializer.dart
+++ b/pkg/front_end/testcases/inference/assert_initializer.dart
@@ -8,14 +8,14 @@ library test;
 T f<T>() => null;
 
 class C {
-  C.expressionOnly() : assert(/*@typeArgs=dynamic*/ f());
+  C.expressionOnly() : assert(/*@typeArgs=bool*/ f());
   C.expressionAndMessage()
-      : assert(/*@typeArgs=dynamic*/ f(), /*@typeArgs=dynamic*/ f());
+      : assert(/*@typeArgs=bool*/ f(), /*@typeArgs=dynamic*/ f());
 }
 
 main() {
   // Test type inference of assert statements just to verify that the behavior
   // is the same.
-  assert(/*@typeArgs=dynamic*/ f());
-  assert(/*@typeArgs=dynamic*/ f(), /*@typeArgs=dynamic*/ f());
+  assert(/*@typeArgs=bool*/ f());
+  assert(/*@typeArgs=bool*/ f(), /*@typeArgs=dynamic*/ f());
 }