MD Settings: Eliminate use of ES6 for Chrome OS

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

Index: chrome/browser/resources/settings/device_page/display.js
diff --git a/chrome/browser/resources/settings/device_page/display.js b/chrome/browser/resources/settings/device_page/display.js
index c2ea9e99d45f98260172d0698543a6b0071a4cb9..c285e43da922bbdde7368b41adbdff37bc95e11e 100644
--- a/chrome/browser/resources/settings/device_page/display.js
+++ b/chrome/browser/resources/settings/device_page/display.js
@@ -153,7 +153,7 @@ Polymer({
   selectedDisplayChanged_: function() {
     // Set |modeValues_| before |selectedModeIndex_| so that the slider updates
     // correctly.
-    let numModes = this.selectedDisplay.modes.length;
+    var numModes = this.selectedDisplay.modes.length;
     if (numModes == 0) {
       this.modeValues_ = [];
       this.selectedModeIndex_ = 0;
@@ -270,15 +270,15 @@ Polymer({
         this.currentSelectedModeIndex_ == -1) {
       // If currentSelectedModeIndex_ == -1, selectedDisplay and
       // selectedModeIndex_ are not in sync.
-      let widthStr = this.selectedDisplay.bounds.width.toString();
-      let heightStr = this.selectedDisplay.bounds.height.toString();
-      return this.i18n('displayResolutionText', widthStr, heightStr);
+      return this.i18n(
+          'displayResolutionText', this.selectedDisplay.bounds.width.toString(),
+          this.selectedDisplay.bounds.height.toString());
     }
-    let mode = this.selectedDisplay.modes[this.selectedModeIndex_];
-    let best =
+    var mode = this.selectedDisplay.modes[this.selectedModeIndex_];
+    var best =
         this.selectedDisplay.isInternal ? mode.uiScale == 1.0 : mode.isNative;
-    let widthStr = mode.width.toString();
-    let heightStr = mode.height.toString();
+    var widthStr = mode.width.toString();

[dpapad, 2017/01/23 19:12:53]

Nit (optional): You can shorten as follows.

var messageId =
    best ? 'displayResolutionTextBest' :
    (mode.isNative ? 'displayResolutionTextNative' : 'displayResolutionText');

return this.i18n(messageId, mode.width.toString(), mode.height.toString());

[stevenjb, 2017/01/24 02:02:03]

I wanted to keep this CL as simple as possible in case we revert later. That
didn't make sense evereywhere, and we probably won't want to just revert, but
I'd still prefer to keep changes to a minimum.

+    var heightStr = mode.height.toString();
     if (best)
       return this.i18n('displayResolutionTextBest', widthStr, heightStr);
     else if (mode.isNative)
@@ -292,7 +292,8 @@ Polymer({
    */
   onSelectDisplay_: function(e) {
     var id = e.detail;
-    for (let display of this.displays) {
+    for (var d = 0; d < this.displays.length; ++d) {

[dpapad, 2017/01/23 19:12:53]

Nit (optional): Same nit as before, 'i' is a more common name for a loop
counter, (then 'j', 'k').

'd' would make more sense if the variable was holding a display variable, but it
is holding just an integer, so IMO 'd' is more confusing than worth it.

[stevenjb, 2017/01/24 02:02:03]

Done.

+      var display = this.displays[d];
       if (id != display.id)
         continue;
       this.currentSelectedModeIndex_ = -1;
@@ -367,7 +368,7 @@ Polymer({
    * @private
    */
   onOrientationChange_: function(event) {
-    let target = /** @type {!HTMLSelectElement} */ (event.target);
+    var target = /** @type {!HTMLSelectElement} */ (event.target);
     /** @type {!chrome.system.display.DisplayProperties} */ var properties = {
       rotation: parseInt(target.value, 10)
     };
@@ -385,7 +386,8 @@ Polymer({
       properties.mirroringSourceId = '';
     } else {
       // Set the mirroringSourceId of the secondary (first non-primary) display.
-      for (var display of this.displays) {
+      for (var d = 0; d < this.displays.length; ++d) {
+        var display = this.displays[d];
         if (display.id != this.primaryDisplayId) {
           id = display.id;
           break;
@@ -412,7 +414,8 @@ Polymer({
     var displayIds = '';
     var primaryDisplay = undefined;
     var selectedDisplay = undefined;
-    for (var display of this.displays) {
+    for (var d = 0; d < this.displays.length; ++d) {
+      var display = this.displays[d];
       if (displayIds)
         displayIds += ',';
       displayIds += display.id;

[dpapad, 2017/01/23 19:12:53]

Why not hold all the display IDs in an array first, and then just do
displayIds.join(',') at line 427? This would simplify the logic (no need to
manually keep track of when to add the comma or not).

[stevenjb, 2017/01/24 02:02:03]

Ditto.