[MD settings] shrink overscroll when scrolling up

chrome/browser/resources/settings/settings_main/settings_main.js

Index: chrome/browser/resources/settings/settings_main/settings_main.js
diff --git a/chrome/browser/resources/settings/settings_main/settings_main.js b/chrome/browser/resources/settings/settings_main/settings_main.js
index 6aa8c1113f14754117d1c1a2bfb7fba3bd9b450b..bf07a8f1bea880f4d05f8704ae8ebe1ad067a511 100644
--- a/chrome/browser/resources/settings/settings_main/settings_main.js
+++ b/chrome/browser/resources/settings/settings_main/settings_main.js
@@ -78,6 +78,20 @@ Polymer({
       settings.navigateTo(this.advancedToggleExpanded_ ?
           settings.Route.ADVANCED : settings.Route.BASIC);
     }.bind(this));
+
+    var mainContainer = this.parentNode.$.mainContainer;

[Dan Beam, 2016/08/03 20:50:32]

can we just use this.parentNode.scroller?

[dschuyler, 2016/08/03 21:46:41]

Done.

+    var overscroll = this.$.overscroll;
+    mainContainer.addEventListener('scroll', function() {

[Dan Beam, 2016/08/03 20:50:32]

can we only listen to scroll when there is padding to remove?

[dschuyler, 2016/08/03 21:46:41]

Done.

+      // TODO(dschuyler): This works okay, but not perfectly with page-up/down
+      // and home/end. It may have to do with the order in which the resize
+      // occurs (relative to the scroll action).

[Dan Beam, 2016/08/03 20:50:32]

^ you can remove this now, I think

[dschuyler, 2016/08/03 21:46:41]

Done.

+      var visibleBottom = mainContainer.scrollTop + mainContainer.clientHeight;
+      var overscrollBottom = overscroll.offsetTop + overscroll.scrollHeight;
+      // How much of the overscroll is visible (may be negative).
+      var visibleOverscroll = overscroll.scrollHeight -
+                              (overscrollBottom - visibleBottom);
+      overscroll.style.paddingBottom = Math.max(0, visibleOverscroll) + 'px';
+    }.bind(this));
   },
 
   /**