Switch variations http headers to only be reported over https.

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>
 
@@ skipping 13 matching lines @@
                             bool incognito,
                             bool uma_enabled,
                             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.
+// specified |url|. Returns true for google.<TLD> and youtube.<TLD> URLs with
+// the https scheme.
 bool ShouldAppendVariationHeaders(const GURL& url);
 
 }  // namespace internal
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADERS_H_