Remove uses of deprecated RegisterDictionaryPref

The override of RegisterDictionaryPref taking a std::unique_ptr<base::Value>
is deprecated in favor of the method taking the base::Value by value.

Convert client code to either not pass default value if the value is just
an empty dictionary (as there is an override doing this). If the dictionary
is not empty, convert the code to create and pass it by value.

This CL was uploaded by git cl split.

Bug: 646113
Change-Id: I0ce16bc2720f325ae5e6349f9acf9829d23f7aa9
Reviewed-on: https://chromium-review.googlesource.com/c/1454582Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629142}

chrome/browser/previews/previews_lite_page_decider.cc

@@ -177,8 +177,7 @@ PreviewsLitePageDecider::~PreviewsLitePageDecider() = default;
 void PreviewsLitePageDecider::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(kUserNeedsNotification, true);
-  registry->RegisterDictionaryPref(kHostBlacklist,
-                                   std::make_unique<base::DictionaryValue>());
+  registry->RegisterDictionaryPref(kHostBlacklist);
 }
 
 // static