Enable Whatsapp calls activity -- no root

Hi folks,
As we saw last days , a fellow guy here
discovered a hidden activity in whatsapp that has
calling feature.
even if you didn't get an invitation for the feature
you still can get this hidden activity and amaze
your friends
or maybe you will be a lucky 5.0 lollipop user that
gets an invitation.
**This method is not like the old ones at all**
**This method makes the calls activity your
home of whatsapp forever**. By editing AndroidManifest.xml of whatsapp.

Requirements:

1. Latest Whatsapp apk
2. ApkTool ( HERE)
3. Basic knowledge of decomipling
4. Basic knowlegde of editing xml files
5. notepad++

Steps :
1. Decompile whatsapp
2. open AndroidManifest.xml
3. search for :
Code:
     <activity
android:configChanges="keyboard|
keyboardHidden|orientation|screenLayout|
screenSize|smallestScreenSize|uiMode"
android:hardwareAccelerated="false"
android:name="com.whatsapp.Main">
           <intent-filter>
                <action
android:name="android.intent.action.MAIN"
/>
               <category
android:name="android.intent.category.LAU
NCHER"/>
                <category
android:name="android.intent.category.MUL
TIWINDOW_LAUNCHER"/>
            </intent-filter>
        </activity>
4. change it to :
Code:
<activity android:configChanges="keyboard|
keyboardHidden|orientation|screenLayout|
screenSize|smallestScreenSize|uiMode"
android:hardwareAccelerated="false"
android:name="com.whatsapp.Main"/>
5. Then search for this line
Code:
        <activity
android:configChanges="keyboard|
keyboardHidden|orientation|screenLayout|
screenSize|smallestScreenSize|uiMode"
android:label="@string/app_name"
android:launchMode="singleTask"
android:name="com.whatsapp.HomeActivity
" android:theme="@style/
Theme.App.Home"/>
6. change to :
Code:
        <activity
android:configChanges="keyboard|
keyboardHidden|orientation|screenLayout|
screenSize|smallestScreenSize|uiMode"
android:label="@string/app_name"
android:launchMode="singleTask"
android:name="com.whatsapp.HomeActivity
" android:theme="@style/
Theme.App.Home">
   <intent-filter>
              <action
android:name="android.intent.action.MAIN"
/>
                <category
android:name="android.intent.category.LAU
NCHER"/>
                <category
android:name="android.intent.category.MUL
TIWINDOW_LAUNCHER"/>
         </intent-filter>
     </activity>
7. Now compile and sign
8. Uninstall the old whatsapp
9. Install the modified one
10. Voila !

**If you are lazy a modified version is available
HERE (Thanks @ Uncertified Robot over @xda developers )**