aj-proof '++' expressions

Author: etpinard

Diff for: src/traces/scattergl/index.js

@@ -126,10 +126,11 @@ function calc(gd, trace) {
 
     // stash scene ref
     stash._scene = scene;
-    stash.index = scene.count++;
+    stash.index = scene.count;
     stash.x = x;
     stash.y = y;
     stash.positions = positions;
+    scene.count++;
 
     return [{x: false, y: false, t: stash, trace: trace}];
 }

Diff for: src/traces/scatterpolargl/index.js

@@ -161,7 +161,8 @@ function plot(gd, subplot, cdata) {
         stash.theta = thetaArray;
         stash.positions = positions;
         stash._scene = scene;
-        stash.index = scene.count++;
+        stash.index = scene.count;
+        scene.count++;
     });
 
     return ScatterGl.plot(gd, subplot, cdata);