Fixed the bug that caused extension options not to fit their overlays properly when zoomed.

chrome/browser/resources/extensions/extension_options_overlay.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('extensions', function() {
   'use strict';
 
   /**
    * The ExtensionOptionsOverlay will show an extension's options page using
    * an <extensionoptions> element.
@@ skipping 109 matching lines @@
       // undesirable effects.
       var animation = null;
 
       /**
        * Resize the overlay if the <extensionoptions> changes preferred size.
        * @param {{width: number, height: number}} evt
        */
       extensionoptions.onpreferredsizechanged = function(evt) {
         var oldWidth = parseInt(overlayStyle.width, 10);
         var oldHeight = parseInt(overlayStyle.height, 10);
-        var newWidth = Math.max(evt.width, minWidth);
-        var newHeight = Math.min(evt.height, maxHeight);
+        // The overlay must be slightly larger than the extension options to
+        // avoid creating scrollbars.
+        var newWidth = Math.max(evt.width + 2, minWidth);

[not at google - send to devlin, 2015/02/18 18:00:12]

Could you explain where the value of 2 comes from, e.g. why not 1?

[paulmeyer, 2015/02/18 18:14:11]

2 pixels allows the overlay a 1 pixel border around the extension options (i.e.
1 per top, bottom, left, right). Adding only 1 pixel for width/height still
results in scrollbars appearing for some zoom levels.

[not at google - send to devlin, 2015/02/18 19:19:10]

Ok, thanks for explaining.

Why is the pixel needed at all? The scrollbar thing sounds pretty unfortunate
but adding a pixel seems... well, a hack. I'm just wondering if this could be
some rounding issue, e.g. if you rounded up evt.height then it would work
(though it does seem like you're doing this already in the event).

Another option would be to force there to be no scrollbars with overflow:hidden
on the overlay, but that's also a bit hacky.

[paulmeyer, 2015/02/19 18:42:58]

It looks like there is a problem with the preferred size coming in from blink
where for some zoom levels the size is too small, and so scrollbars appear. I'll
put a TODO here for now and then investigate the problem with the size in Blink.

+        var newHeight = Math.min(evt.height + 2, maxHeight);
 
         // animationTime is the amount of time in ms that will be used to resize
         // the overlay. It is calculated by multiplying the pythagorean distance
         // between old and the new size (in px) with a constant speed of
         // 0.25 ms/px.
         var loading = document.documentElement.classList.contains('loading');
         var animationTime = loading ? 0 :
             0.25 * Math.sqrt(Math.pow(newWidth - oldWidth, 2) +
                              Math.pow(newHeight - oldHeight, 2));
 
@@ skipping 51 matching lines @@
           /** @type {HTMLDivElement} */($('extension-options-overlay')) :
           null);
     }
   };
 
   // Export
   return {
     ExtensionOptionsOverlay: ExtensionOptionsOverlay
   };
 });