Checks for valid CObject lengths in native API.

runtime/include/dart_native_api.h

Index: runtime/include/dart_native_api.h
diff --git a/runtime/include/dart_native_api.h b/runtime/include/dart_native_api.h
index 7691d5ca7bbd8dcf4fb2f65353c0f940965fc9c1..cdfc5df777a3823bf4e89a19fa21f7eb2178386a 100644
--- a/runtime/include/dart_native_api.h
+++ b/runtime/include/dart_native_api.h
@@ -53,17 +53,17 @@ typedef struct _Dart_CObject {
     char* as_string;
     char* as_bigint;
     struct {
-      int length;
+      intptr_t length;
       struct _Dart_CObject** values;
     } as_array;
     struct {
       Dart_TypedData_Type type;
-      int length;
+      intptr_t length;
       uint8_t* values;
     } as_typed_data;
     struct {
       Dart_TypedData_Type type;
-      int length;
+      intptr_t length;
       uint8_t* data;
       void* peer;
       Dart_WeakPersistentHandleFinalizer callback;