MD Settings: fix overflow scrolling for <settings-dialog>

chrome/browser/resources/settings/settings_dialog.js

 // Copyright 2016 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.
 
 /**
  * @fileoverview 'settings-dialog' is a component for showing a modal dialog.
  */
 Polymer({
   is: 'settings-dialog',
 
@@ skipping 12 matching lines @@
 
     /** @override */
     withBackdrop: {
       type: Boolean,
       value: true,
     },
   },
 
   behaviors: [Polymer.PaperDialogBehavior],
 
+  /** @override */
+  center: function() {
+    Polymer.IronFitBehavior.center.call(this);
+
+    this.$$('.body-container').style.maxHeight = this.offsetHeight -
+        (this.$$('.title-container').offsetHeight +
+         this.$$('.button-container').offsetHeight +
+         this.$$('.footer-container').offsetHeight) + 'px';

[Dan Beam, 2016/05/13 01:42:40]

Do you hate this? (y/n) _

[dpapad, 2016/05/13 18:14:03]

Well, it is a bit complicated at first sight. My main concern is not so much
this particular calculation but the overall complexity of the desired dialog
scrolling behavior. Issues I see so far for example,

1) clipping issue at http://imgur.com/HshMbbE (after patching this CL).
2) The "Clear browsing data" dialog looks very odd (too small for the amount of
content it has), see http://imgur.com/XOVA4oY. The scrollbar and the buttons are
adjacent at the corner which seems weird IMO. 

Scrolling the entire dialog (current behavior) seems more robust to resizing,
but I understand that the current spec calls for scrolling the body only, so we
should try to achieve that behavior, but without creating corner cases that
current behavior does not have.

[dpapad, 2016/05/13 18:20:33]

FYI regarding the clipping issue, I had filed
https://github.com/PolymerElements/paper-dialog-behavior/issues/83 in the past.
Polymer team tried to fix, but this caused other bugs and was reverted, and
eventually it was left up to users to specify overflow.

[Dan Beam, 2016/05/17 19:26:12]

fixed
CBD should now look better, but without a border between the scrollable area and
the button strip, we're bound to end up in odd states.  this is not different
from options.
the new patchset should be a good blend of simple-ish and good UX

+  },
+
   /** @return {!PaperIconButtonElement} */
   getCloseButton: function() {
     return this.$.close;
   },
 });