title: Measuring text width/height without rendering
body: <p>Is there any way to get an estimate for text width without rendering the actual elements? Something like canvas TextMetrics?</p>
  
  <p>Case: I need to estimate element heights for ReactList. To do that I'd need to know roughly how much space the text elements will need (or how many lines will they span).</p>
  
  <p>eg.</p>
  
  <pre><code>render(){
      return &lt;div&gt;&lt;SomeComponentWithKnownDims/&gt;&lt;p&gt;{this.props.someText}&lt;/p&gt;&lt;/div&gt;;
  }
  </code></pre>
  
  <p>If I knew how wide someText would be rendered into one line and how long the line would be, I could easily come up with a decent estimate for the components height.</p>
  
  <p>EDIT: Note that this is quite performance critical and <strong>DOM should not be touched</strong></p>