Add other variations (with ids) for NTPSnippets to chrome://flags

components/variations/variations_associated_data.h

Index: components/variations/variations_associated_data.h
diff --git a/components/variations/variations_associated_data.h b/components/variations/variations_associated_data.h
index b60192ea2b3c0a684829b0c01f91dfb33e965708..41471034f5f7c2920d150247a1ccfcfb8fb19b2b 100644
--- a/components/variations/variations_associated_data.h
+++ b/components/variations/variations_associated_data.h
@@ -6,7 +6,9 @@
 #define COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
 
 #include <map>
+#include <memory>
 #include <string>
+#include <vector>
 
 #include "base/metrics/field_trial.h"
 #include "components/variations/active_field_trials.h"
@@ -48,6 +50,7 @@ struct Feature;
 namespace variations {
 
 typedef int VariationID;
+class VariationsHttpHeaderProvider;
 
 const VariationID EMPTY_ID = 0;
 
@@ -71,6 +74,13 @@ enum IDCollectionKey {
   ID_COLLECTION_COUNT,
 };
 
+// Forces the |variation_ids| (possible extended by |command_line_variation_ids|
+// passed in a command line flag) into a VariationsHttpHeaderProvider that it
+// returns.
+VariationsHttpHeaderProvider* ForceVariationIDsForHttpHeaders(
+    std::vector<std::string> variation_ids,
+    std::string command_line_variation_ids);
+
 // Associate a variations::VariationID value with a FieldTrial group for
 // collection |key|. If an id was previously set for |trial_name| and
 // |group_name|, this does nothing. The group is denoted by |trial_name| and