title: WebGLInput.captureAllKeyboardInput strange behaviour. Can enable, but cannot disable
body: <p>I am experiencing very strange behaviour of WebGLInput.
  I have a website with a WebGL Unity build. By default WebGL is capturing all keyboard inputs. However, I have to use input fields in my html.</p>
  
  <p>So at first I disable WebGLInput and it works:</p>
  
  <pre class="lang-js prettyprint-override"><code>private void Start()
  {
  #if !UNITY_EDITOR &amp;&amp; UNITY_WEBGL 
       WebGLInput.captureAllKeyboardInput = false;
  #endif
  }
  </code></pre>
  
  <p>Then using function below I send a message to unity to toggle the keyboard input. And it works at first to enable it, but it doesn't disable it!</p>
  
  <pre class="lang-js prettyprint-override"><code>document.addEventListener('click', function(e) {
      if (e.target.id == "#canvas") {
          this.FocusCanvas("1");
      } else {
          this.FocusCanvas("0");
      }
  }.bind(this), false);
  </code></pre>
  
  <p>This is my unity code to toggle WebGLInput:</p>
  
  <pre class="lang-js prettyprint-override"><code>public void FocusCanvas(string focus)
  {
      #if !UNITY_EDITOR &amp;&amp; UNITY_WEBGL
          if (focus == "0") {
              WebGLInput.captureAllKeyboardInput = false;
          } else {
              WebGLInput.captureAllKeyboardInput = true;
          }
      #endif
  }
  </code></pre>
  
  <p>I debugged it as far as I could and I'm more than sure that method is triggered and everything is executed. But disabling captureAllKeyboardInput does not work. Have someone encountered such problem? if so, please let me know what am I doing wrong? </p>