Migrate data reduction proxy statistics prefs to profile

components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc
index 2d9d8174b86c65b1f8695e6f57d27ad21cb19145..20f9465af5cf15ac9a3b4e882025254a6e8c958a 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc
@@ -88,5 +88,10 @@ const char kHttpReceivedContentLength[] = "http_received_content_length";
 // received over the network.
 const char kHttpOriginalContentLength[] = "http_original_content_length";
 
+// A boolean specifying whether the data reduction proxy statistics preferences
+// have migrated from local state to the profile.
+const char kStatisticsPrefsMigrated[] =
+    "data_reduction.statistics_prefs_migrated";
+
 }  // namespace prefs
 }  // namespace data_reduction_proxy