Standardize StringToInt{,64} interface.

base/string_piece.h

Index: base/string_piece.h
diff --git a/base/string_piece.h b/base/string_piece.h
index 278c7b692ae4750673dee32abcc2cc69c1631d3b..f1d34739c77a3422315a99e343eac367827e8965 100644
--- a/base/string_piece.h
+++ b/base/string_piece.h
@@ -60,6 +60,9 @@ class BASE_EXPORT StringPiece {
     : ptr_(str.data()), length_(str.size()) { }
   StringPiece(const char* offset, size_type len)
     : ptr_(offset), length_(len) { }
+  StringPiece(const std::string::const_iterator& begin,
+              const std::string::const_iterator& end)
+      : ptr_(&(*begin)), length_((size_type)(end - begin)) { }
 
   // data() may return a pointer to a buffer with embedded NULs, and the
   // returned buffer may or may not be null terminated.  Therefore it is
@@ -197,6 +200,9 @@ class BASE_EXPORT StringPiece16 {
       : ptr_(str.data()), length_(str.size()) { }
   StringPiece16(const char16* offset, size_type len)
       : ptr_(offset), length_(len) { }
+  StringPiece16(const string16::const_iterator& begin,
+                const string16::const_iterator& end)
+      : ptr_(&(*begin)), length_((size_type)(end - begin)) { }
 
   // data() may return a pointer to a buffer with embedded NULs, and the
   // returned buffer may or may not be null terminated.  Therefore it is