Polymer: Remove unused app-layout element

third_party/polymer/v1_0/components-chromium/app-layout/app-scroll-effects/effects/blend-background-extracted.js

-/**
-   * While scrolling down, fade in the rear background layer and fade out the front background
-   * layer (opacity interpolated based on scroll position).
-   */
-  Polymer.AppLayout.registerEffect('blend-background', {
-    /** @this Polymer.AppLayout.ElementWithBackground */
-    setUp: function setUp() {
-      var fx = {};
-      fx.backgroundFrontLayer = this._getDOMRef('backgroundFrontLayer');
-      fx.backgroundRearLayer = this._getDOMRef('backgroundRearLayer');
-      fx.backgroundFrontLayer.style.willChange = 'opacity';
-      fx.backgroundFrontLayer.style.transform = 'translateZ(0)';
-      fx.backgroundRearLayer.style.willChange = 'opacity';
-      fx.backgroundRearLayer.style.transform = 'translateZ(0)';
-      fx.backgroundRearLayer.style.opacity = 0;
-      this._fxBlendBackground = fx;
-    },
-    /** @this Polymer.AppLayout.ElementWithBackground */
-    run: function run(p, y) {
-      var fx = this._fxBlendBackground;
-      fx.backgroundFrontLayer.style.opacity = 1 - p;
-      fx.backgroundRearLayer.style.opacity = p;
-    },
-    /** @this Polymer.AppLayout.ElementWithBackground */
-    tearDown: function tearDown() {
-      delete this._fxBlendBackground;
-    }
-  });