Revert of Restrict transmission of external exp ids to signed in users.

components/variations/net/variations_http_headers.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADERS_H_
 #define COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADERS_H_
 
 #include <set>
 #include <string>
 
 namespace net {
 class HttpRequestHeaders;
 }
 
 class GURL;
 
 namespace variations {
 
 // Adds Chrome experiment and metrics state as custom headers to |headers|.
-// The content of the headers will depend on |incognito|, |uma_enabled| and
-// |is_signed_in| parameters. It is fine to pass false for |is_signed_in| if the
-// state is not known to the caller. This will prevent addition of ids of type
-// GOOGLE_WEB_PROPERTIES_SIGNED_IN, which is not the case for any ids that come
-// from the variations server. These headers are never transmitted to non-Google
-// web sites, which is checked based on the destination |url|.
+// Some headers may not be set given the |incognito| mode or whether
+// the user has |uma_enabled|.  Also, we never transmit headers to non-Google
+// sites, which is checked based on the destination |url|.
 void AppendVariationHeaders(const GURL& url,
                             bool incognito,
                             bool uma_enabled,
-                            bool is_signed_in,
                             net::HttpRequestHeaders* headers);
 
 // Returns the HTTP header names which are added by AppendVariationHeaders().
 std::set<std::string> GetVariationHeaderNames();
 
 namespace internal {
 
 // Checks whether variation headers should be appended to requests to the
 // specified |url|. Returns true for google.<TLD> and youtube.<TLD> URLs.
 bool ShouldAppendVariationHeaders(const GURL& url);
 
 }  // namespace internal
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADERS_H_