title: Why the difference in using common and post for changing the ContentType should affect the request payload / form data?
body: <p>If I use the following:</p>
  
  <p>a) </p>
  
  <pre><code>angularApp.config(function ($httpProvider) {
    $httpProvider.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded';
    $httpProvider.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';
    $httpProvider.defaults.headers.common['Accept'] = 'application/json';
    $httpProvider.defaults.transformRequest = function(data) {
        if (data === undefined) {
            return data;
        }
        return $.param(data);
    }
  });
  </code></pre>
  
  <p>versus</p>
  
  <p>b)</p>
  
  <pre><code>angularApp.config(function ($httpProvider) {
    $httpProvider.defaults.headers.common['Content-Type'] = 'application/x-www-form-urlencoded';
    $httpProvider.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';
    $httpProvider.defaults.headers.common['Accept'] = 'application/json';
    $httpProvider.defaults.transformRequest = function(data) {
        if (data === undefined) {
            return data;
        }
        return $.param(data);
    }
  });
  </code></pre>
  
  <p>And then when I use a <code>$http.post</code> or a <code>$resource</code> that uses <code>POST</code></p>
  
  <p>a) is what I want because I get this in the Chrome Dev Tools: </p>
  
  <pre><code>  Form Data:
      User[old_password]:xxx
      User[new_password]:yyyy
      User[new_password_confirm]:yyyy
  </code></pre>
  
  <p>b) is NOT what I want because I get this in the Chrome Dev Tools:</p>
  
  <pre><code>Request Payload:
  User%5Bold_password%5D=xxx&amp;User%5Bnew_password%5D=yyyy&amp;User%5Bnew_password_confirm%5D=yyyy
  </code></pre>
  
  <p>This puzzles me because I expect common to apply for everything including post.</p>
  
  <p>The only difference between a) and b) is b) has</p>
  
  <pre><code>  $httpProvider.defaults.headers.**common**['Content-Type'] = 'application/x-www-form-urlencoded';
  </code></pre>
  
  <p>I am using angular <code>1.2.6</code>.</p>
  
  <p>Issue also occurs in <code>1.2.9</code></p>
  
  <p>Please advise.</p>