do not try to clear ax layers on first render

- this can speed up Axes.doTicks by 50ms on 50x50 subplots grids

Author: etpinard

src/plot_api/plot_api.js

@@ -347,7 +347,7 @@ exports.plot = function(gd, data, layout, config) {
 
     // draw ticks, titles, and calculate axis scaling (._b, ._m)
     function drawAxes() {
-        return Axes.doTicks(gd, 'redraw');
+        return Axes.doTicks(gd, graphWasEmpty ? '' : 'redraw');
     }
 
     // Now plot the data

src/plots/cartesian/axes.js

@@ -1539,10 +1539,8 @@ axes.doTicks = function(gd, axid, skipTitle) {
                 return function() {
                     if(!ax._id) return;
                     var axDone = axes.doTicks(gd, ax._id);
-                    if(axid === 'redraw') {
-                        ax._r = ax.range.slice();
-                        ax._rl = Lib.simpleMap(ax._r, ax.r2l);
-                    }
+                    ax._r = ax.range.slice();
+                    ax._rl = Lib.simpleMap(ax._r, ax.r2l);
                     return axDone;
                 };
             }));