dart2js cps: More type rules in type propagation.

pkg/compiler/lib/src/cps_ir/type_mask_system.dart

Index: pkg/compiler/lib/src/cps_ir/type_mask_system.dart
diff --git a/pkg/compiler/lib/src/cps_ir/type_mask_system.dart b/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
index 0a21c3f657152af2c858ed7ef23181c27822e378..5b30cafa0f93a8876ec464fbec642c576d94894f 100644
--- a/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
+++ b/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
@@ -559,11 +559,8 @@ class TypeMaskSystem implements AbstractValueDomain {
     if (isDefinitelyString(type)) {
       return stringType;
     }
-    if (type.satisfies(helpers.typedArrayClass, classWorld)) {
-      if (type.satisfies(helpers.typedArrayOfIntClass, classWorld)) {
-        return intType;
-      }
-      return numType;
+    if (type.satisfies(helpers.jsIndexingBehaviorInterface, classWorld)) {
+      return getInvokeReturnType(new Selector.index(), type);
     }
     return dynamicType;
   }