See: the 'waterfall' attribute in https://polymerelements.github.io/app-layout/templates/test-drive/ We don't want to pull all of app-layout into the binary just for that, so we should be able to achieve the same effect with https://elements.polymer-project.org/elements/iron-scroll-target-behavior.
The following revision refers to this bug: https://chromium.googlesource.com/chromium/src.git/+/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7 commit cb8aa763196dbb73c7aa724bd3bc7374a2a540a7 Author: calamity <calamity@chromium.org> Date: Wed Aug 24 11:51:34 2016 [MD History] Add shadow to toolbar on scroll. This CL adds the IronScrollTargetBehavior to history-app so that it can listen to scroll events from the currently active history view and render a shadow beneath the toolbar when the scroll isn't at the top. BUG= 638114 CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation Review-Url: https://codereview.chromium.org/2253083003 Cr-Commit-Position: refs/heads/master@{#414048} [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/app.crisper.js [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/app.html [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/app.js [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/app.vulcanized.html [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/list_container.js [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/browser/resources/md_history/synced_device_manager.js [modify] https://crrev.com/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7/chrome/test/data/webui/md_history/history_list_test.js
Comment 1 by tsergeant@chromium.org
, Aug 16 2016