MD Settings: Display: Fix runtime error

chrome/browser/resources/settings/device_page/layout_behavior.js

Index: chrome/browser/resources/settings/device_page/layout_behavior.js
diff --git a/chrome/browser/resources/settings/device_page/layout_behavior.js b/chrome/browser/resources/settings/device_page/layout_behavior.js
index 33e2162e7018d5708102b7e6ed868cb94407eef1..90d5990aeb2f17ea1f2cdb797d105c8dfb7305a0 100644
--- a/chrome/browser/resources/settings/device_page/layout_behavior.js
+++ b/chrome/browser/resources/settings/device_page/layout_behavior.js
@@ -83,6 +83,10 @@ var LayoutBehavior = {
    */
   updateDisplayBounds(id, newBounds) {

[dpapad, 2016/11/23 01:48:51]

I am confused by the mixing of ES6 and non-ES6 syntax for defining methods.
|LayoutBehavior| is not a proper ES6 class. Can we simply be consistent with the
rest of this file, and use ES6 method syntax only in proper ES6 classes?

updateDisplayBounds: function(id, newBounds) {
  ...
},

[stevenjb, 2016/11/23 17:40:46]

Oversight on my part. I wish we could enforce this. Fixed.

     this.dragLayoutId = id;
+    if (this.displays.length < 2) {

[dpapad, 2016/11/23 01:48:51]

Where is |this.displays| defined? Did not find it in this file. Is it assuming
that elements that implement the behavior have a |displays| member var? Can we
infer that information without creating such implicit contracts between this
behavior and the classes that inherit from it?

Perhaps the following condition is equivalent?

this.displayBoundsMap_.size < 2

[stevenjb, 2016/11/23 17:40:46]

Ah, you're right, I should actually move this check up to display_layout.js
(which calls updateDisplayBounds). We don't actually need to update dragBounds
or dragLayoutId with just one display.

Fixed, thanks.

+      this.dragBounds_ = newBounds;
+      return newBounds;
+    }
 
     // Find the closest parent.
     var closestId = this.findClosest_(id, newBounds);