Add more API fuzzing and fix the issues encountered.

runtime/bin/builtin_natives.cc

 // Copyright (c) 2012, 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 "bin/builtin.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include "bin/dartutils.h"
@@ skipping 111 matching lines @@
 
 
 void FUNCTION_NAME(Logger_PrintString)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Builtin::PrintString(stdout, Dart_GetNativeArgument(args, 0));
   Dart_ExitScope();
 }
 
 void FUNCTION_NAME(Exit)(Dart_NativeArguments args) {
   Dart_EnterScope();
-  int64_t status = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 0));
+  int64_t status = 0;
+  // Ignore result if passing invalid argument and just exit 0.
+  DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 0), &status);
   Dart_ExitScope();
   exit(status);
 }
 
 
 void Builtin::SetNativeResolver(Builtin::BuiltinLibraryId id) {
   Dart_Handle url;
   if (id == Builtin::kBuiltinLibrary) {
     url = Dart_NewString(DartUtils::kBuiltinLibURL);
   } else {
     ASSERT(id == Builtin::kIOLibrary);
     url = Dart_NewString(DartUtils::kIOLibURL);
   }
   Dart_Handle builtin_lib = Dart_LookupLibrary(url);
   DART_CHECK_VALID(builtin_lib);
   // Setup the native resolver for built in library functions.
   Dart_Handle result = Dart_SetNativeResolver(builtin_lib, NativeLookup);
   DART_CHECK_VALID(result);
 }