Move kDataReductionProxy registration to the data_reduction_proxy component.

ios/chrome/browser/prefs/browser_prefs.mm

Index: ios/chrome/browser/prefs/browser_prefs.mm
diff --git a/ios/chrome/browser/prefs/browser_prefs.mm b/ios/chrome/browser/prefs/browser_prefs.mm
index 017eb4e345428880307be534679c053538ca7ce4..7e61b40f8433d0172f2f69ac1b8879e4f89a03a4 100644
--- a/ios/chrome/browser/prefs/browser_prefs.mm
+++ b/ios/chrome/browser/prefs/browser_prefs.mm
@@ -8,7 +8,6 @@
 #include "components/autofill/core/browser/autofill_manager.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.h"
-#include "components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h"
 #include "components/dom_distiller/core/distilled_page_prefs.h"
 #include "components/enhanced_bookmarks/bookmark_server_cluster_service.h"
 #include "components/gcm_driver/gcm_channel_status_syncer.h"
@@ -67,11 +66,6 @@ void RegisterLocalStatePrefs(PrefRegistrySimple* registry) {
   [OmniboxGeolocationLocalState registerLocalState:registry];
   [MemoryDebuggerManager registerLocalState:registry];
 
-  // TODO(crbug.com/557814): data_reduction_proxy::prefs::kDataReductionProxy
-  // should be registered by data_reduction_proxy::RegisterPrefs() instead of
-  // here.
-  registry->RegisterStringPref(data_reduction_proxy::prefs::kDataReductionProxy,
-                               std::string());
   data_reduction_proxy::RegisterPrefs(registry);
 
   // TODO(shreyasv): Remove this in M49 as almost all users would have the