Revert of MD Settings: long dialog body should have overscroll line.

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js

Index: ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
diff --git a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
index a84993e7e1fd185f8552ef825dac109ac91dce87..d15ed9b8173a769d12afe886806d1509a99cfffc 100644
--- a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
+++ b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
@@ -29,16 +29,7 @@
       type: Boolean,
       value: false,
     },
-
-    showScrollBorders: {
-      type: Boolean,
-      value: false,
-      reflectToAttribute: true,
-    },
   },
-
-  /** @private {?IntersectionObserver} */
-  intersectionObserver_: null,
 
   /** @override */
   ready: function() {
@@ -48,35 +39,6 @@
       if (!this.ignorePopstate && this.open)
         this.cancel();
     }.bind(this));
-  },
-
-  /** @override */
-  attached: function() {
-    if (this.showScrollBorders) {
-      var bodyContainer = this.$$('.body-container');
-
-      var callback = function(entries) {
-        assert(entries.length == 1);
-        bodyContainer.classList.toggle(
-            'bottom-scrollable', entries[0].intersectionRatio == 0);
-      };
-
-      this.intersectionObserver_ = new IntersectionObserver(
-          callback,
-          /** @type {IntersectionObserverInit} */ ({
-            root: bodyContainer,
-            threshold: 0,
-          }));
-      this.intersectionObserver_.observe(this.$.bodyBottomMarker);
-    }
-  },
-
-  /** @override */
-  detached: function() {
-    if (this.intersectionObserver_) {
-      this.intersectionObserver_.disconnect();
-      this.intersectionObserver_ = null;
-    }
   },
 
   cancel: function() {