Fix bug in Dart API Dart_IntegerToUint64: crash on negative Mints

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "lib/stacktrace.h"
 #include "platform/assert.h"
@@ skipping 2123 matching lines @@
     }
   }
   // Slow path for Mints and Bigints.
   DARTSCOPE(thread);
   const Integer& int_obj = Api::UnwrapIntegerHandle(Z, integer);
   if (int_obj.IsNull()) {
     RETURN_TYPE_ERROR(Z, integer, Integer);
   }
   if (int_obj.IsSmi()) {
     ASSERT(int_obj.IsNegative());
-  } else if (int_obj.IsMint() && !int_obj.IsNegative()) {
-    *value = int_obj.AsInt64Value();
-    return Api::Success();
+  } else if (int_obj.IsMint()) {
+    if (!int_obj.IsNegative()) {
+      *value = int_obj.AsInt64Value();
+      return Api::Success();
+    }
   } else {
     const Bigint& bigint = Bigint::Cast(int_obj);
     if (bigint.FitsIntoUint64()) {
       *value = bigint.AsUint64Value();
       return Api::Success();
     }
   }
   return Api::NewError("%s: Integer %s cannot be represented as a uint64_t.",
                        CURRENT_FUNC, int_obj.ToCString());
 }
@@ skipping 4538 matching lines @@
 #endif
 }
 
 DART_EXPORT void Dart_DumpNativeStackTrace(void* context) {
 #ifndef PRODUCT
   Profiler::DumpStackTrace(context);
 #endif
 }
 
 }  // namespace dart