Refactor der::Input helper methods into new constructors

net/cert/internal/test_helpers.cc

Index: net/cert/internal/test_helpers.cc
diff --git a/net/cert/internal/test_helpers.cc b/net/cert/internal/test_helpers.cc
index 18e1f6ca74e72fd1744dcd19560293b16206d665..4194ae3e6a44665b2f05131160511d30e94dee65 100644
--- a/net/cert/internal/test_helpers.cc
+++ b/net/cert/internal/test_helpers.cc
@@ -32,12 +32,8 @@ bool operator==(const Input& a, const Input& b) {
 
 }  // namespace der
 
-der::Input InputFromString(const std::string* s) {
-  return der::Input(reinterpret_cast<const uint8_t*>(s->data()), s->size());
-}
-
 der::Input SequenceValueFromString(const std::string* s) {
-  der::Parser parser(InputFromString(s));
+  der::Parser parser((der::Input(s)));
   der::Input data;
   if (!parser.ReadTag(der::kSequence, &data)) {
     ADD_FAILURE();