[SalesForce] reuse the dependency logic of State and Country picklists from Account/Contact in a Apex Classes

I have enabled the State and Country picklists in Salesforce and
I was trying to get/create the same kind of country and state picklist with dependency from Contact in a visual force page.

I have done the below steps:

From the controller i tried to create the country and state picklists in the custom visual force page.

Add Contact Visual force Page:

<apex:page StandardController="CustomObject__c" extensions="AddContactController">
<apex:form >
    <apex:pageBlock title="Add Contact" mode="edit">
        <apex:pageBlockButtons >
            <apex:commandButton action="{!save}" value="Save"/>
        </apex:pageBlockButtons>
        <apex:pageBlockSection title="Contact Details" columns="2">
              <apex:selectList id="states" value="{!myContact.MailingState}" size="1" required="false">
              <apex:selectOptions value="{!states}"/>
            </apex:selectList>
              <apex:selectList id="countries" value="{!myContact.MailingCountry}" size="1" required="true">
              <apex:selectOptions value="{!countries}"/>
            </apex:selectList>
        </apex:pageBlockSection>
    </apex:pageBlock>
</apex:form>

AddContactController Apex Class

public class AddContactController {
ApexPages.StandardController stdCtrl;
public Contact myContact{ get; private set;}

public AddContactController(ApexPages.StandardController std) {
    stdCtrl = std;
    myContact = new Contact();
}   
public List<SelectOption> countries { get{ return getCountries(); }set; }
public List<SelectOption> states{ get{ return getStates(); }set; }

public List<SelectOption> getCountries()
{
  Schema.sObjectType objType = Contact.getSObjectType();
  Schema.DescribeSObjectResult objDescribe = objType.getDescribe();
  map<String, Schema.SObjectField> fieldMap = objDescribe.fields.getMap();
  list<Schema.PicklistEntry> values = fieldMap.get('MailingCountryCode').getDescribe().getPickListValues();

  List<SelectOption> options = new List<SelectOption>();
  for (Schema.PicklistEntry v : values){
    options.add(new SelectOption(v.getValue(), v.getLabel()));
  };
  return options;
}

public List<SelectOption> getStates()
{
  Schema.sObjectType objType = Contact.getSObjectType();
  Schema.DescribeSObjectResult objDescribe = objType.getDescribe();
  map<String, Schema.SObjectField> fieldMap = objDescribe.fields.getMap();
  list<Schema.PicklistEntry> values = fieldMap.get('MailingStateCode').getDescribe().getPickListValues();
  List<SelectOption> options = new List<SelectOption>();
  for (Schema.PicklistEntry v : values){
    options.add(new SelectOption(v.getLabel(), v.getvalue()));
  };
  return options;
}}

The above code populates the entire countries and states in the custom visual force page from the Contact State/Country picklists but doesn't have dependency on the country and state.

Is there any way to get the dependency and by country onchange i could show respective states in custom visual force page instead of manually configuring the dependency or using external packages(Provenworks).

Thanks in advance .