Convert some base/prefs/ methods to scoped_ptr instead of bare ptr

BUG=

Review URL: https://codereview.chromium.org/1160403002

Cr-Commit-Position: refs/heads/master@{#336412}
diff --git a/base/prefs/overlay_user_pref_store.cc b/base/prefs/overlay_user_pref_store.cc
index 4c236f1..d76b537 100644
--- a/base/prefs/overlay_user_pref_store.cc
+++ b/base/prefs/overlay_user_pref_store.cc
@@ -58,31 +58,31 @@
     return false;
 
   *result = underlay_value->DeepCopy();
-  overlay_.SetValue(key, *result);
+  overlay_.SetValue(key, make_scoped_ptr(*result));
   return true;
 }
 
 void OverlayUserPrefStore::SetValue(const std::string& key,
-                                    base::Value* value,
+                                    scoped_ptr<base::Value> value,
                                     uint32 flags) {
   if (!ShallBeStoredInOverlay(key)) {
-    underlay_->SetValue(GetUnderlayKey(key), value, flags);
+    underlay_->SetValue(GetUnderlayKey(key), value.Pass(), flags);
     return;
   }
 
-  if (overlay_.SetValue(key, value))
+  if (overlay_.SetValue(key, value.Pass()))
     ReportValueChanged(key, flags);
 }
 
 void OverlayUserPrefStore::SetValueSilently(const std::string& key,
-                                            base::Value* value,
+                                            scoped_ptr<base::Value> value,
                                             uint32 flags) {
   if (!ShallBeStoredInOverlay(key)) {
-    underlay_->SetValueSilently(GetUnderlayKey(key), value, flags);
+    underlay_->SetValueSilently(GetUnderlayKey(key), value.Pass(), flags);
     return;
   }
 
-  overlay_.SetValue(key, value);
+  overlay_.SetValue(key, value.Pass());
 }
 
 void OverlayUserPrefStore::RemoveValue(const std::string& key, uint32 flags) {