Fix bug in Dart API Dart_IntegerToUint64: crash on negative Mints

runtime/vm/dart_api_impl_test.cc

Index: runtime/vm/dart_api_impl_test.cc
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index 60ff7cc45175886143c6a720e6e805a8d7dab3f0..13142c8987a897c02f32452d27131a7f65216f87 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -868,6 +868,7 @@ TEST_CASE(IntegerValues) {
   const int64_t kIntegerVal2 = 0xffffffff;
   const char* kIntegerVal3 = "0x123456789123456789123456789";
   const uint64_t kIntegerVal4 = 0xffffffffffffffff;
+  const int64_t kIntegerVal5 = -0x7fffffffffffffff;
 
   Dart_Handle val1 = Dart_NewInteger(kIntegerVal1);
   EXPECT(Dart_IsInteger(val1));
@@ -914,6 +915,12 @@ TEST_CASE(IntegerValues) {
   uint64_t out5 = 0;
   result = Dart_IntegerToUint64(val5, &out5);
   EXPECT(Dart_IsError(result));
+
+  Dart_Handle val6 = Dart_NewInteger(kIntegerVal5);
+  EXPECT_VALID(val6);
+  uint64_t out6 = 0;
+  result = Dart_IntegerToUint64(val6, &out6);
+  EXPECT(Dart_IsError(result));
 }
 
 TEST_CASE(IntegerFitsIntoInt64) {