Add iterator range constructors to StringPiece.

base/string_piece.h

Index: base/string_piece.h
diff --git a/base/string_piece.h b/base/string_piece.h
index f80ca5bb3e367157de6f82ddc6784f8a2b4567a2..6a9528f50dc3b2e04dc44f3a925a3f34132bc507 100644
--- a/base/string_piece.h
+++ b/base/string_piece.h
@@ -65,6 +65,14 @@ template <typename STRING_TYPE> class StringPieceDetail {
   StringPieceDetail(const STRING_TYPE& str)
       : ptr_(str.data()),
         length_(str.size()) {}
+  StringPieceDetail(const typename STRING_TYPE::const_iterator& begin,
+                    const typename STRING_TYPE::const_iterator& end)
+      : ptr_(begin == end ? NULL : &*begin),
+        length_(end - begin) {}
+  StringPieceDetail(const typename STRING_TYPE::iterator& begin,
+                    const typename STRING_TYPE::iterator& end)
+      : ptr_(begin == end ? NULL : &*begin),
+        length_(end - begin) {}
   StringPieceDetail(const value_type* offset, size_type len)
       : ptr_(offset),
         length_(len) {}
@@ -168,6 +176,12 @@ template <typename STRING_TYPE> class BasicStringPiece :
       : internal::StringPieceDetail<STRING_TYPE>(str) {}
   BasicStringPiece(const STRING_TYPE& str)
       : internal::StringPieceDetail<STRING_TYPE>(str) {}
+  BasicStringPiece(const typename STRING_TYPE::const_iterator& begin,
+                   const typename STRING_TYPE::const_iterator& end)
+      : internal::StringPieceDetail<STRING_TYPE>(begin, end) {}
+  BasicStringPiece(const typename STRING_TYPE::iterator& begin,
+                   const typename STRING_TYPE::iterator& end)
+      : internal::StringPieceDetail<STRING_TYPE>(begin, end) {}
   BasicStringPiece(const value_type* offset, size_type len)
       : internal::StringPieceDetail<STRING_TYPE>(offset, len) {}
 };
@@ -182,6 +196,12 @@ template <> class BASE_EXPORT BasicStringPiece<std::string> :
       : internal::StringPieceDetail<std::string>(str) {}
   BasicStringPiece(const std::string& str)
       : internal::StringPieceDetail<std::string>(str) {}
+  BasicStringPiece(const std::string::const_iterator& begin,
+                   const std::string::const_iterator& end)
+      : internal::StringPieceDetail<std::string>(begin, end) {}
+  BasicStringPiece(const std::string::iterator& begin,
+                   const std::string::iterator& end)
+      : internal::StringPieceDetail<std::string>(begin, end) {}
   BasicStringPiece(const char* offset, size_type len)
       : internal::StringPieceDetail<std::string>(offset, len) {}