Implement md5 hash in crypto library.

lib/crypto/sha1.dart

Index: lib/crypto/sha1.dart
diff --git a/lib/crypto/sha1.dart b/lib/crypto/sha1.dart
index cc0d198715ade81b8d95497f1321e59210c2b891..41e66369056f5f11961fadc5a53a14c5cd650de8 100644
--- a/lib/crypto/sha1.dart
+++ b/lib/crypto/sha1.dart
@@ -3,9 +3,9 @@
 // BSD-style license that can be found in the LICENSE file.
 
 // The SHA1 hasher is used to compute an SHA1 message digest.
-class _SHA1 extends _SHAHashBase implements SHA1 {
+class _SHA1 extends _HashBase implements SHA1 {
   // Construct a SHA1 hasher object.
-  _SHA1() : _w = new List(80), super(16, 5) {
+  _SHA1() : _w = new List(80), super(16, 5, true) {
     _h[0] = 0x67452301;
     _h[1] = 0xEFCDAB89;
     _h[2] = 0x98BADCFE;
@@ -18,13 +18,6 @@ class _SHA1 extends _SHAHashBase implements SHA1 {
     return new SHA1();
   }
 
-  // Rotate left limiting to unsigned 32-bit values.
-  int _rotl32(int val, int shift) {
-    var mod_shift = shift & 31;
-    return ((val << mod_shift) & _MASK_32) |
-        ((val & _MASK_32) >> (32 - mod_shift));
-  }
-
   // Compute one iteration of the SHA1 algorithm with a chunk of
   // 16 32-bit pieces.
   void _updateHash(List<int> m) {