Use low entropy for studies that send experiment IDs to Google properties.

components/variations/service/variations_service.h

Index: components/variations/service/variations_service.h
diff --git a/components/variations/service/variations_service.h b/components/variations/service/variations_service.h
index 4d3c282ff640cf9350c5526e2be015eb51323982..74357b5f14da9242c5fef9c69b7b3120357df04e 100644
--- a/components/variations/service/variations_service.h
+++ b/components/variations/service/variations_service.h
@@ -178,6 +178,12 @@ class VariationsService
                          bool is_delta_compressed,
                          bool is_gzip_compressed);
 
+  // Create an entropy provider based on low entropy. This is used to create
+  // trials for studies that should only depend on low entropy, such as studies
+  // that send experiment IDs to Google web properties. Virtual for testing.
+  virtual std::unique_ptr<const base::FieldTrial::EntropyProvider>
+  CreateLowEntropyProvider();
+
   // Creates the VariationsService with the given |local_state| prefs service
   // and |state_manager|. Does not take ownership of |state_manager|. Caller
   // should ensure that |state_manager| is valid for the lifetime of this class.