Restrict transmission of external exp ids to signed in users.

chrome/browser/android/contextualsearch/contextual_search_delegate.cc

Index: chrome/browser/android/contextualsearch/contextual_search_delegate.cc
diff --git a/chrome/browser/android/contextualsearch/contextual_search_delegate.cc b/chrome/browser/android/contextualsearch/contextual_search_delegate.cc
index f170cd054592562ec444ceae0a4a2a609bcf4aa7..30f18c8f45f22750eb65a2e3c4379b6378eb22eb 100644
--- a/chrome/browser/android/contextualsearch/contextual_search_delegate.cc
+++ b/chrome/browser/android/contextualsearch/contextual_search_delegate.cc
@@ -136,10 +136,13 @@ void ContextualSearchDelegate::ContinueSearchTermResolutionRequest() {
 
   // Add Chrome experiment state to the request headers.
   net::HttpRequestHeaders headers;
+  // Note: It's fine to pass in |is_signed_in| false, which does not affect
+  // transmission of experiment ids coming from the variations server.
+  bool is_signed_in = false;
   variations::AppendVariationHeaders(
       search_term_fetcher_->GetOriginalURL(),
       false,  // Impossible to be incognito at this point.
-      false, &headers);
+      false, is_signed_in, &headers);
   search_term_fetcher_->SetExtraRequestHeaders(headers.ToString());
 
   SetDiscourseContextAndAddToHeader(*context_);