[plot] set minimum marquee size

Users must draw a marquee box with diagonal size of atleast 7.5
pixels.  This prevents clicks from being translated to zooms on
the plot.  Because startMarquee triggers a plot history update.
endMarquee must remove the plot history update when preventing
marqueeZoom.  This has a side effect of causing a requery for
data, but is a simple enough solution for now.

Fixes #2002.

circle.yml

@@ -1,6 +1,6 @@
 machine:
   node:
-    version: 4.7.0
+    version: 8.11.0
 
 dependencies:
   pre:
@@ -24,4 +24,4 @@ test:
 general:
   branches:
     ignore:
-      - gh-pages
+      - gh-pages

src/plugins/plot/src/plot/MCTPlotController.js

@@ -220,6 +220,7 @@ define([
             return;
         }
         this.marquee.end = this.positionOverPlot;
+        this.marquee.endPixels = this.positionOverElement;
     };
 
     MCTPlotController.prototype.startMarquee = function ($event) {
@@ -227,6 +228,8 @@ define([
         if (this.positionOverPlot) {
             this.freeze();
             this.marquee = {
+                startPixels: this.positionOverElement,
+                endPixels: this.positionOverElement,
                 start: this.positionOverPlot,
                 end: this.positionOverPlot,
                 color: [1, 1, 1, 0.5]
@@ -237,8 +240,14 @@ define([
     };
 
     MCTPlotController.prototype.endMarquee = function () {
-        if (this.marquee.start.x !== this.marquee.end.x &&
-            this.marquee.start.y !== this.marquee.end.y) {
+        var startPixels = this.marquee.startPixels;
+        var endPixels = this.marquee.endPixels;
+        var marqueeDistance = Math.sqrt(
+            Math.pow(startPixels.x - endPixels.x, 2) +
+            Math.pow(startPixels.y - endPixels.y, 2)
+        );
+        // Don't zoom if mouse moved less than 7.5 pixels.
+        if (marqueeDistance > 7.5) {
             this.$scope.xAxis.set('displayRange', {
                 min: Math.min(this.marquee.start.x, this.marquee.end.x),
                 max: Math.max(this.marquee.start.x, this.marquee.end.x)
@@ -248,6 +257,10 @@ define([
                 max: Math.max(this.marquee.start.y, this.marquee.end.y)
             });
             this.$scope.$emit('user:viewport:change:end');
+        } else {
+            // A history entry is created by startMarquee, need to remove
+            // if marquee zoom doesn't occur.
+            this.back();
         }
         this.$scope.rectangles = [];
         this.marquee = undefined;