title: not able to find iframe in protractor tests
body: <p>I am trying to find an element which is within iframe. So i try to switch to iframe.</p>
  
  <p>The iframe in html:</p>
  
  <pre><code>&lt;iframe id="id_of_iframe"  data-app-id="com.s-h.ph.pr" class="external-app ng-scope ng-isolate-scope" ng-if="!vm.appDisabled"  ng-attr-sandbox="{{vm.iframeConfig.sandbox ? vm.iframeConfig.sandbox : ''}}" tp-onload="vm.sendCurrentRouteToIFrame()" style="border: none; border-width: 0; height: 100%; width: 100%; display: block;" sandbox="allow-forms allow-popups allow-pointer-lock allow-same-origin allow-scripts allow-top-navigation allow-modals"&gt;&lt;/iframe&gt; 
  </code></pre>
  
  <p>code used:</p>
  
  <pre><code> browser.switchTo().frame('id_of_iframe');
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code> Failed: no such frame
        (Session info: chrome=61.0.3163.100)
        (Driver info: chromedriver=2.32.498550 (9dec58e66c31bcc53a9ce3c7226f0c1c58
  10906a),platform=Windows NT 6.1.7601 SP1 x86_64)
    Stack:
      NoSuchFrameError: no such frame
        (Session info: chrome=61.0.3163.100)
        (Driver info: chromedriver=2.32.498550 (9dec58e66c31bcc53a9ce3c7226f0c1c58
  10906a),platform=Windows NT 6.1.7601 SP1 x86_64)
          at WebDriverError (C:\Users\z002ex9t\AppData\Roaming\npm\node_modules\pr
  otractor\node_modules\selenium-webdriver\lib\error.js:27:5)
          at NoSuchFrameError (C:\Users\z002ex9t\AppData\Roaming\npm\node_modules\
  protractor\node_modules\selenium-webdriver\lib\error.js:180:5)
          at Object.checkLegacyResponse (C:\Users\z002ex9t\AppData\Roaming\npm\nod
  e_modules\protractor\node_modules\selenium-webdriver\lib\error.js:505:15)
          at parseHttpResponse (C:\Users\z002ex9t\AppData\Roaming\npm\node_modules
  \protractor\node_modules\selenium-webdriver\lib\http.js:509:13)
          at doSend.then.response (C:\Users\z002ex9t\AppData\Roaming\npm\node_modu
  les\protractor\node_modules\selenium-webdriver\lib\http.js:440:13)
          at process._tickCallback (internal/process/next_tick.js:109:7)
  </code></pre>
  
  <p>I am using the following versions :
  "protractor": "5.1.2",
  "jasmine": "2.8.0"
   webdriver-manager 12.0.6</p>
  
  <p>Any idea how to solve this issue?</p>
  
  <p>Thanks in advance.</p>