MD Settings: Remove paper-header-panel, use IntersectionObserver.

chrome/browser/resources/settings/settings_ui/settings_ui.js

 // Copyright 2015 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-ui' implements the UI for the Settings page.
  *
  * Example:
  *
@@ skipping 142 matching lines @@
           googleDrive: false,
         },
 // </if>
       };
     }
 
     this.showAndroidApps_ = loadTimeData.valueExists('androidAppsAllowed') &&
         loadTimeData.getBoolean('androidAppsAllowed');
   },
 
+  intersectionObserver_: null,

[scottchen, 2017/03/28 22:06:55]

Do you need @private here?

[dpapad, 2017/03/28 22:10:57]

This needs "@private {?IntersectionObserver}", but I have not added it yet,
since the compilation fails anyway. Will add once the JS Compiler externs issue
is resolved.

[dpapad, 2017/03/29 22:17:10]

Done.

+
   /** @override */
   attached: function() {
     setTimeout(function() {
       chrome.send(
           'metricsHandler:recordTime',
           ['Settings.TimeUntilInteractive', window.performance.now()]);
     });
     // Preload bold Roboto so it doesn't load and flicker the first time used.
     document.fonts.load('bold 12px Roboto');
-    settings.setGlobalScrollTarget(this.$.headerPanel.scroller);
+    settings.setGlobalScrollTarget(this.$.container);
+
+    this.setupDropShadow_();

[Dan Beam, 2017/03/29 13:19:55]

just make this part of attached rather than a separate method (just delete
L176-180)

[dpapad, 2017/03/29 22:17:10]

Done.

+  },
+
+  /** @private */
+  setupDropShadow_: function() {
+    var callback = function(entries) {
+      assert(entries.length == 1);
+      entries[0].intersectionRatio == 0 ?
+          this.$.dropShadow.classList.add('has-shadow') :
+          this.$.dropShadow.classList.remove('has-shadow');

[Dan Beam, 2017/03/29 13:19:55]

this.$.dropShadow.classList.toggle('has-shadow', entries[0].intersectionRatio ==
0);

[dpapad, 2017/03/29 22:17:10]

Done.

+    }.bind(this);
+
+    this.intersectionObserver_ = new IntersectionObserver(callback, {
+      root: this.$.container,
+      threshold: 0,
+    });
+    this.intersectionObserver_.observe(this.$.intersectionProbe);
   },
 
   /** @override */
   detached: function() {
     settings.resetRouteForTesting();
+    this.intersectionObserver_.disconnect();
+    this.intersectionObserver_ = null;
   },
 
   /** @param {!settings.Route} route */
   currentRouteChanged: function(route) {
     var urlSearchQuery = settings.getQueryParameters().get('search') || '';
     if (urlSearchQuery == this.lastSearchQuery_)
       return;
 
     this.lastSearchQuery_ = urlSearchQuery;
 
@@ skipping 54 matching lines @@
   onMenuButtonTap_: function() {
     this.$.drawer.toggle();
   },
 
   /** @private */
   directionDelegateChanged_: function() {
     this.$.drawer.align = this.directionDelegate.isRtl() ?
         'right' : 'left';
   },
 });