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

chrome/browser/resources/extensions/extension_options_overlay.js

Index: chrome/browser/resources/extensions/extension_options_overlay.js
diff --git a/chrome/browser/resources/extensions/extension_options_overlay.js b/chrome/browser/resources/extensions/extension_options_overlay.js
index 07684a98bef5cbc3f8f0e889039b4c9c808b894e..1e559227dc8cb260ba035d61369a8e289b33df30 100644
--- a/chrome/browser/resources/extensions/extension_options_overlay.js
+++ b/chrome/browser/resources/extensions/extension_options_overlay.js
@@ -127,8 +127,10 @@ cr.define('extensions', function() {
       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