Some perf improvements when updating the layers list, also throttled color picker.

src/components/fields/ColorField.jsx

@@ -2,6 +2,7 @@ import React from 'react'
 import Color from 'color'
 import ChromePicker from 'react-color/lib/components/chrome/Chrome'
 import PropTypes from 'prop-types'
+import lodash from 'lodash';
 
 function formatColor(color) {
   const rgb = color.rgb
@@ -23,6 +24,15 @@ class ColorField extends React.Component {
     pickerOpened: false
   }
 
+  constructor () {
+    super();
+    this.onChangeNoCheck = lodash.throttle(this.onChangeNoCheck, 1000/30);
+  }
+
+  onChangeNoCheck (v) {
+    this.props.onChange(formatColor(v));
+  }
+
   //TODO: I much rather would do this with absolute positioning
   //but I am too stupid to get it to work together with fixed position
   //and scrollbars so I have to fallback to JavaScript
@@ -82,7 +92,7 @@ class ColorField extends React.Component {
       }}>
       <ChromePicker
         color={currentColor}
-        onChange={c => this.props.onChange(formatColor(c))}
+        onChange={c => this.onChangeNoCheck(formatColor(c))}
       />
       <div
         className="maputnik-color-picker-offset"