make surface calc step its own module (to be used in heatmapgl too)

Author: etpinard

src/traces/surface/calc.js

@@ -0,0 +1,18 @@
+/**
+* Copyright 2012-2015, Plotly, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the MIT license found in the
+* LICENSE file in the root directory of this source tree.
+*/
+
+
+'use strict';
+
+var Colorscale = require('../../components/colorscale');
+
+
+// Compute auto-z and autocolorscale if applicable
+module.exports = function calc(gd, trace) {
+    Colorscale.calc(trace, trace.z, '', 'z');
+};

src/traces/surface/index.js

@@ -32,9 +32,4 @@ Surface.supplyDefaults = require('./defaults');
 
 Surface.colorbar = require('../heatmap/colorbar');
 
-Surface.calc = function(gd, trace) {
-
-    // auto-z and autocolorscale if applicable
-    Plotly.Colorscale.calc(trace, trace.z, '', 'z');
-
-};
+Surface.calc = require('./calc');