Refactor der::Input helper methods into new constructors

net/der/input.cc

Index: net/der/input.cc
diff --git a/net/der/input.cc b/net/der/input.cc
index 5065ccaca93e9bdc3ffc06b5af2eaa332d57f1ae..871f9f4ec7dc29a52d645f9c2194c2795d559394 100644
--- a/net/der/input.cc
+++ b/net/der/input.cc
@@ -19,6 +19,11 @@ Input::Input() : data_(nullptr), len_(0) {
 Input::Input(const uint8_t* data, size_t len) : data_(data), len_(len) {
 }
 
+Input::Input(const base::StringPiece& in)
+    : data_(reinterpret_cast<const uint8_t*>(in.data())), len_(in.length()) {}
+
+Input::Input(const std::string* s) : Input(base::StringPiece(*s)) {}
+
 bool Input::Equals(const Input& other) const {
   if (len_ != other.len_)
     return false;
@@ -29,6 +34,10 @@ std::string Input::AsString() const {
   return std::string(reinterpret_cast<const char*>(data_), len_);
 }
 
+base::StringPiece Input::AsStringPiece() const {
+  return base::StringPiece(reinterpret_cast<const char*>(data_), len_);
+}
+
 bool operator<(const Input& lhs, const Input& rhs) {
   return std::lexicographical_compare(
       lhs.UnsafeData(), lhs.UnsafeData() + lhs.Length(), rhs.UnsafeData(),