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..82690a726b71269779ea0b7ac106fb89b7ef1937 100644
--- a/chrome/browser/resources/settings/device_page/layout_behavior.js
+++ b/chrome/browser/resources/settings/device_page/layout_behavior.js
@@ -81,11 +81,12 @@ var LayoutBehavior = {
    *     bounds for the display.
    * @return {!chrome.system.display.Bounds}
    */
-  updateDisplayBounds(id, newBounds) {
+  updateDisplayBounds: function(id, newBounds) {
     this.dragLayoutId = id;
 
     // Find the closest parent.
     var closestId = this.findClosest_(id, newBounds);

[dpapad, 2016/11/23 18:18:43]

Nit (optional):
var closestId = assert(this.findClosest_(id, newBounds));

[stevenjb, 2016/11/23 18:44:32]

Personal nit: I'm not a huge fan of wrapping essential logic inside of an assert
outside of tests. Partly because in C++ if you accidentally do that with a
DCHECK the logic is never run in production code, but also because I find it
harder to read. We rarely do that in Chrome C++ code, although I realize this
may be a common pattern in JS.

[Dan Beam, 2016/11/23 20:46:55]

JS != C++

+    assert(closestId);
 
     // Find the closest edge.
     var closestBounds = this.getCalculatedDisplayBounds(closestId);
@@ -128,7 +129,7 @@ var LayoutBehavior = {
    * Called when dragging ends. Sends the updated layout to chrome.
    * @param {string} id
    */
-  finishUpdateDisplayBounds(id) {
+  finishUpdateDisplayBounds: function(id) {
     this.highlightEdge_('', undefined);  // Remove any highlights.
     if (id != this.dragLayoutId || !this.dragBounds_ ||
         !this.dragLayoutPosition_) {