Revert "Remove NullPointerException."

runtime/lib/regexp.cc

Index: runtime/lib/regexp.cc
diff --git a/runtime/lib/regexp.cc b/runtime/lib/regexp.cc
index 7054257bea660287579020e258c380e64e5141bb..00088b5b0253c38e8962eabf9b607e61080b9ba1 100644
--- a/runtime/lib/regexp.cc
+++ b/runtime/lib/regexp.cc
@@ -12,10 +12,19 @@
 
 namespace dart {
 
+static void CheckAndThrowExceptionIfNull(const Instance& obj) {
+  if (obj.IsNull()) {
+    GrowableArray<const Object*> args;
+    Exceptions::ThrowByType(Exceptions::kNullPointer, args);
+  }
+}
+
 
 DEFINE_NATIVE_ENTRY(JSSyntaxRegExp_factory, 4) {
   ASSERT(AbstractTypeArguments::CheckedHandle(
       arguments->NativeArgAt(0)).IsNull());
+  const Instance& arg1 = Instance::CheckedHandle(arguments->NativeArgAt(1));
+  CheckAndThrowExceptionIfNull(arg1);
   GET_NATIVE_ARGUMENT(String, pattern, arguments->NativeArgAt(1));
   GET_NATIVE_ARGUMENT(Instance, handle_multi_line, arguments->NativeArgAt(2));
   GET_NATIVE_ARGUMENT(Instance, handle_ignore_case, arguments->NativeArgAt(3));
@@ -66,6 +75,8 @@ DEFINE_NATIVE_ENTRY(JSSyntaxRegExp_getGroupCount, 1) {
 DEFINE_NATIVE_ENTRY(JSSyntaxRegExp_ExecuteMatch, 3) {
   const JSRegExp& regexp = JSRegExp::CheckedHandle(arguments->NativeArgAt(0));
   ASSERT(!regexp.IsNull());
+  const Instance& arg1 = Instance::CheckedHandle(arguments->NativeArgAt(1));
+  CheckAndThrowExceptionIfNull(arg1);
   GET_NATIVE_ARGUMENT(String, str, arguments->NativeArgAt(1));
   GET_NATIVE_ARGUMENT(Smi, start_index, arguments->NativeArgAt(2));
   return Jscre::Execute(regexp, str, start_index.Value());