Remove uses of deprecated override of PrefValueMap::SetValue

Convert client of the deprecated of PrefValueMap::SetValue taking
a std::unique_ptr<base::Value> to the recommended override taking
a base::Value directly.

The conversion is done using the following rules:

- If the value is built inline using std::make_unique<base::Value>
  then change to just construct a base::Value directly,

- If the value is built use base::Value::CreateDeepCopy(), then
  change to use base::Clone() which returns a base::Value instead
  of a std::unique_ptr<base::Value>,

- If the std::unique_ptr<base::Value> is just forwarded by the
  caller, dcheck it is not null (the check was present in the old
  method implementation) and use base::Value::FromUniquePtrValue
  to convert the std::unique_ptr<base::Value> to a base::Value.

This CL fixes uses in src/chrome/browser/spellchecker.

This CL was uploaded by git cl split.

Bug: 646113
Change-Id: I0cc2c207c8e1fdf11710c29aa0ca78fb982758a8
Reviewed-on: https://chromium-review.googlesource.com/c/1446356Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627979}

chrome/browser/spellchecker/spellcheck_language_policy_handler.cc

@@ -41,21 +41,19 @@ void SpellcheckLanguagePolicyHandler::ApplyPolicySettings(
 
   const base::Value::ListStorage& languages = value->GetList();
 
-  std::unique_ptr<base::ListValue> forced_language_list =
-      std::make_unique<base::ListValue>();
+  std::vector<base::Value> forced_language_list;
   for (const base::Value& language : languages) {
     std::string current_language =
         spellcheck::GetCorrespondingSpellCheckLanguage(
             base::TrimWhitespaceASCII(language.GetString(), base::TRIM_ALL));
     if (!current_language.empty()) {
-      forced_language_list->GetList().push_back(base::Value(current_language));
+      forced_language_list.emplace_back(std::move(current_language));
     } else {
       LOG(WARNING) << "Unknown language requested: \"" << language << "\"";
     }
   }
 
-  prefs->SetValue(spellcheck::prefs::kSpellCheckEnable,
-                  std::make_unique<base::Value>(true));
+  prefs->SetValue(spellcheck::prefs::kSpellCheckEnable, base::Value(true));
   prefs->SetValue(spellcheck::prefs::kSpellCheckForcedDictionaries,
-                  std::move(forced_language_list));
+                  base::Value(std::move(forced_language_list)));
 }