[CodeHealth] Remove uses of ListValue::begin()/end() in /dbus.

This CL removes calls to these deprecated member functions. It also
converts to the newer "for" loop syntax when possible, along with
other minor cleanup.

This CL was uploaded by git cl split.

R=satorux@chromium.org

Bug: 1187107
Change-Id: I6a7a39dc479265bef7c6df50b6805e61dffcceb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2877403
Auto-Submit: David Bertoni <dbertoni@chromium.org>
Reviewed-by: Satoru Takabayashi <satorux@chromium.org>
Commit-Queue: Satoru Takabayashi <satorux@chromium.org>
Cr-Commit-Position: refs/heads/master@{#880159}

dbus/values_util.cc

@@ -270,7 +270,7 @@ void AppendValueData(MessageWriter* writer, const base::Value& value) {
       value.GetAsList(&list);
       dbus::MessageWriter array_writer(nullptr);
       writer->OpenArray("v", &array_writer);
-      for (const auto& value_in_list : *list) {
+      for (const auto& value_in_list : list->GetList()) {
         AppendValueDataAsVariant(&array_writer, value_in_list);
       }
       writer->CloseContainer(&array_writer);