Restrict transmission of external exp ids to signed in users.

components/variations/net/variations_http_headers.h

Index: components/variations/net/variations_http_headers.h
diff --git a/components/variations/net/variations_http_headers.h b/components/variations/net/variations_http_headers.h
index d6280e56e8e0584e4cdad1a803ca7a38e46b88b7..5c799319ce4e6d240da892fd7aa8c443619f0a73 100644
--- a/components/variations/net/variations_http_headers.h
+++ b/components/variations/net/variations_http_headers.h
@@ -17,12 +17,13 @@ class GURL;
 namespace variations {
 
 // Adds Chrome experiment and metrics state as custom headers to |headers|.
-// 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
+// The content of the headers will depend on |incognito|, |uma_enabled| and
+// |is_signed_in| parameters. 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().