Move kDataReductionProxy registration to the data_reduction_proxy component.

The pref data_reduction_proxy::prefs::kDataReductionProxy should have
been part of data_reduction_proxy::RegisterPrefs() to avoid having
all embedder register it manually just before call said function.

BUG=557814

Review URL: https://codereview.chromium.org/1463973003

Cr-Commit-Position: refs/heads/master@{#361358}

chrome/browser/io_thread.cc

@@ -42,7 +42,6 @@
 #include "chrome/common/pref_names.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
-#include "components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h"
 #include "components/data_usage/core/data_use_aggregator.h"
 #include "components/data_usage/core/data_use_amortizer.h"
 #include "components/data_usage/core/data_use_annotator.h"
@@ -1013,8 +1012,6 @@ void IOThread::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterStringPref(prefs::kGSSAPILibraryName, std::string());
   registry->RegisterStringPref(prefs::kAuthAndroidNegotiateAccountType,
                                std::string());
-  registry->RegisterStringPref(
-      data_reduction_proxy::prefs::kDataReductionProxy, std::string());
   registry->RegisterBooleanPref(prefs::kEnableReferrers, true);
   data_reduction_proxy::RegisterPrefs(registry);
   registry->RegisterBooleanPref(prefs::kBuiltInDnsClientEnabled, true);

components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.cc

@@ -125,6 +125,7 @@ void RegisterSimpleProfilePrefs(PrefRegistrySimple* registry) {
 // Add any new data reduction proxy prefs to the |pref_map_| or the
 // |list_pref_map_| in Init() of DataReductionProxyCompressionStats.
 void RegisterPrefs(PrefRegistrySimple* registry) {
+  registry->RegisterStringPref(prefs::kDataReductionProxy, std::string());
   registry->RegisterInt64Pref(
       prefs::kHttpReceivedContentLength, 0);
   registry->RegisterInt64Pref(

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