Use DVLOG in configuration_policy_handler_list.cc

Currently LOG(WARNING) is used which shows a long list of warning
during browser startup. Use VLOG(1) so that it does not show up by
default perstyleguide at src/styleguide/c++/c++.md#logging

R=atwilson@chromium.org

Change-Id: Ia32bcfc012583535d028a51165f4aa779ef12954
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2208018Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772024}

components/policy/core/browser/configuration_policy_handler_list.cc

@@ -87,7 +87,7 @@ bool ConfigurationPolicyHandlerList::IsPlatformDevicePolicy(
   if (!policy_details) {
     const std::string prefix(kPolicyCommentPrefix);
     if (iter->first.compare(0, prefix.length(), prefix) != 0) {
-      LOG(WARNING) << "Unknown policy: " << iter->first;
+      DVLOG(1) << "Unknown policy: " << iter->first;
     }
     return false;
   }