Re-implement http sessions.

sdk/lib/io/http_headers.dart

Index: sdk/lib/io/http_headers.dart
diff --git a/sdk/lib/io/http_headers.dart b/sdk/lib/io/http_headers.dart
index de6379b8a4561d602be5acae3778996a362d58f6..a8aae51f2e35e76ee8c4d861fba0b6b464f65c5b 100644
--- a/sdk/lib/io/http_headers.dart
+++ b/sdk/lib/io/http_headers.dart
@@ -405,6 +405,71 @@ class _HttpHeaders implements HttpHeaders {
     return sb.toString();
   }
 
+  List<Cookie> _parseCookies() {
+    // Parse a Cookie header value according to the rules in RFC 6265.
+    var cookies = new List<Cookie>();
+    void parseCookieString(String s) {
+      int index = 0;
+
+      bool done() => index == s.length;
+
+      void skipWS() {
+        while (!done()) {
+         if (s[index] != " " && s[index] != "\t") return;
+         index++;
+        }
+      }
+
+      String parseName() {
+        int start = index;
+        while (!done()) {
+          if (s[index] == " " || s[index] == "\t" || s[index] == "=") break;
+          index++;
+        }
+        return s.substring(start, index).toLowerCase();
+      }
+
+      String parseValue() {
+        int start = index;
+        while (!done()) {
+          if (s[index] == " " || s[index] == "\t" || s[index] == ";") break;
+          index++;
+        }
+        return s.substring(start, index).toLowerCase();
+      }
+
+      void expect(String expected) {
+        if (done()) {
+          throw new HttpException("Failed to parse header value [$s]");
+        }
+        if (s[index] != expected) {
+          throw new HttpException("Failed to parse header value [$s]");
+        }
+        index++;
+      }
+
+      while (!done()) {
+        skipWS();
+        if (done()) return;
+        String name = parseName();
+        skipWS();
+        expect("=");
+        skipWS();
+        String value = parseValue();
+        cookies.add(new _Cookie(name, value));
+        skipWS();
+        if (done()) return;
+        expect(";");
+      }
+    }
+    List<String> values = this["cookie"];
+    if (values != null) {
+      values.forEach((headerValue) => parseCookieString(headerValue));
+    }
+    return cookies;
+  }
+
+
   bool _mutable = true;  // Are the headers currently mutable?
   Map<String, List<String>> _headers;
   List<String> _noFoldingHeaders;