[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..2fda937476231a7e4cbce3c3271bfb874e697a1c 100644
--- a/chrome/browser/resources/settings/settings_main/settings_main.js
+++ b/chrome/browser/resources/settings/settings_main/settings_main.js
@@ -71,6 +71,12 @@ Polymer({
     },
   },
 
+  /**
+   * The smallest value for the height of the overscroll padding.
+   * @const {number}
+   */
+  MINIMUM_OVERSCROLL: 64,

[Dan Beam, 2016/08/02 21:57:36]

can you make this private?

[dschuyler, 2016/08/02 22:32:44]

Done. And then ended up removing it.

+
   /** @override */
   attached: function() {
     document.addEventListener('toggle-advanced-page', function(e) {
@@ -78,6 +84,18 @@ Polymer({
       settings.navigateTo(this.advancedToggleExpanded_ ?
           settings.Route.ADVANCED : settings.Route.BASIC);
     }.bind(this));
+
+    var mainContainer = this.domHost.$$('paper-header-panel').$.mainContainer;
+    mainContainer.addEventListener('scroll', function() {
+      let visibleBottom = mainContainer.scrollTop + mainContainer.clientHeight;
+      let overscrollBottom = this.$.overscroll.offsetTop +

[Dan Beam, 2016/08/02 21:57:36]

nit: var overscroll = this.$.overscroll; (and re-use)

[dschuyler, 2016/08/02 22:32:44]

Done.

+          this.$.overscroll.scrollHeight;
+      // How much of the overscroll is visible (may be negative).
+      let visibleOverscroll = this.$.overscroll.scrollHeight -
+                     (overscrollBottom - visibleBottom);

[Dan Beam, 2016/08/02 21:57:36]

indent off

[dschuyler, 2016/08/02 22:32:44]

Done.

+      if (visibleOverscroll > this.MINIMUM_OVERSCROLL)
+        this.$.overscroll.style.paddingBottom = visibleOverscroll + 'px';
+    }.bind(this));
   },
 
   /**
@@ -128,7 +146,8 @@ Polymer({
       // Ensure any dom-if reflects the current properties.
       Polymer.dom.flush();
 
-      this.$.overscroll.style.paddingBottom = this.overscrollHeight_() + 'px';
+      this.$.overscroll.style.paddingBottom = Math.max(this.MINIMUM_OVERSCROLL,
+          this.overscrollHeight_()) + 'px';
     }.bind(this));
   },