Have VariationsService get version for simulation callback from client

components/variations/variations_service_client.h

Index: components/variations/variations_service_client.h
diff --git a/components/variations/variations_service_client.h b/components/variations/variations_service_client.h
index 1ac863f95633199f5c3a1ebff85d74a4f14fbfe9..6ddccca2cf6c3c03de8af49af5b8c46e97a8f741 100644
--- a/components/variations/variations_service_client.h
+++ b/components/variations/variations_service_client.h
@@ -7,6 +7,9 @@
 
 #include <string>
 
+#include "base/callback.h"
+#include "base/version.h"
+
 namespace base {
 class SequencedWorkerPool;
 }
@@ -34,6 +37,13 @@ class VariationsServiceClient {
   // tasks that may block.
   virtual base::SequencedWorkerPool* GetBlockingPool() = 0;
 
+  // Returns a callback that when run returns the base::Version to use for
+  // variations seed simulation. VariationsService guarantees that the callback
+  // will be run on the pool returned by
+  // VariationsServiceClient::GetBlockingPool().
+  virtual base::Callback<base::Version(void)>
+  GetVersionForSimulationCallback() = 0;
+
   virtual net::URLRequestContextGetter* GetURLRequestContext() = 0;
   virtual network_time::NetworkTimeTracker* GetNetworkTimeTracker() = 0;