Whitelist cookie controls so changes are persisted

At this point cookie controls setting is exposed only in incognito mode.
This cl makes changes to the setting being persisted across incognito
sessions.

Bug: 967668
Change-Id: Icc42a7365186af5ccc74777236574ee9813ae3a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1844819
Commit-Queue: Huanzhong Huang <huanzhong@chromium.org>
Reviewed-by: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704103}

chrome/browser/prefs/pref_service_incognito_whitelist.cc

@@ -10,6 +10,7 @@
 #include "build/build_config.h"
 #include "chrome/common/pref_names.h"
 #include "components/bookmarks/common/bookmark_pref_names.h"
+#include "components/content_settings/core/common/pref_names.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/rappor/rappor_pref_names.h"
 #include "components/reading_list/core/reading_list_pref_names.h"
@@ -207,6 +208,11 @@ const char* const kPersistentPrefNames[] = {
     ukm::prefs::kUkmClientId,
     ukm::prefs::kUkmUnsentLogStore,
     ukm::prefs::kUkmSessionId,
+
+    // Cookie controls preference is, as in an initial release, surfaced only in
+    // the incognito mode and therefore should be persisted between incognito
+    // sessions.
+    prefs::kCookieControlsMode,
 };
 
 }  // namespace