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

chrome/browser/resources/settings/settings_ui/settings_ui.html

 <link rel="import" href="chrome://resources/cr_elements/cr_drawer/cr_drawer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-header-panel/paper-header-panel.html">
 <link rel="import" href="../direction_delegate.html">
 <link rel="import" href="../global_scroll_target_behavior.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../icons.html">
 <link rel="import" href="../settings_main/settings_main.html">
 <link rel="import" href="../settings_menu/settings_menu.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="../prefs/prefs.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_vars_css.html">
 
 <if expr="chromeos">
 <link rel="import" href="chrome://resources/cr_elements/network/cr_onc_types.html">
 </if>
 
 <dom-module id="settings-ui">
   <template>
     <style include="settings-shared">
       :host {
         @apply(--layout-fit);
-        --paper-header-panel-waterfall-container: {
-          overflow-x: auto;  /* Undo paper-header-panel default of 'hidden'. */
-          overflow-y: overlay;
-        };
         -webkit-user-select: none;
         background-color: var(--settings-background-color);
         color: var(--paper-grey-900);
         display: flex;
         flex-direction: column;
         line-height: 154%; /* Apply 20px line-height to all texts by default. */
         overflow: hidden;  /* Prevent double scroll bar bugs. */
       }
 
       .drawer-header {
         outline: none;
       }
 
-      paper-header-panel {
-        flex: 1;
-      }
-
-      .paper-header {
-        -webkit-padding-start: 24px;
-        align-items: center;
-        border-bottom: var(--settings-separator-line);
-        display: flex;
-        font-size: 123.08%; /* go to 16px from 13px */
-        min-height: 56px;
-      }
-
       .last {
         display: flex;
         justify-content: flex-end;
         width: 100%;
       }
 
       dialog[is='cr-drawer'] {
         z-index: 2;
       }
 
       cr-toolbar {
         @apply(--layout-center);
         --cr-toolbar-field-width: var(--settings-card-max-width);
         --iron-icon-fill-color: white;
         background-color: var(--settings-title-bar-background-color);
         color: white;
         min-height: 56px;
         z-index: 2;
       }
+
+      #container {
+        flex: 1;
+        overflow: overlay;
+      }
+
+      #dropShadow {
+        box-shadow: inset 0 5px 6px -3px rgba(0, 0, 0, 0.4);
+        height: 6px;
+        left: 0;
+        opacity: 0;
+        pointer-events: none;
+        position: absolute;
+        right: 0;
+        top: 56px;
+        transition: opacity 500ms;
+        z-index: 1;
+     }

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

indent off

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

Done.

+
+     #dropShadow.has-shadow {
+       opacity: 1;
+     }
     </style>
     <settings-prefs id="prefs" prefs="{{prefs}}"></settings-prefs>
     <cr-toolbar page-name="$i18n{settings}"
         clear-label="$i18n{clearSearch}"
         search-prompt="$i18n{searchPrompt}"
         on-cr-toolbar-menu-tap="onMenuButtonTap_"
         spinner-active="[[toolbarSpinnerActive_]]"
         menu-label="$i18n{menuButtonLabel}"
         on-search-changed="onSearchChanged_"
         show-menu>
     </cr-toolbar>
     <dialog id="drawer" is="cr-drawer">
       <div class="drawer-header" tabindex="-1">$i18n{settings}</div>
       <div class="drawer-content">
         <template is="dom-if" id="drawerTemplate">
           <settings-menu page-visibility="[[pageVisibility_]]"
               show-android-apps="[[showAndroidApps_]]"
               on-iron-activate="onIronActivate_"
               advanced-opened="{{advancedOpened_}}">
           </settings-menu>
         </template>
       </div>
     </dialog>
-    <paper-header-panel id="headerPanel" mode="waterfall">
+    <div id="dropShadow"></div>
+    <div id="container">
+      <!-- Used by IntersectionObserver, has a 0px height intentionally -->
+      <div id="intersectionProbe"></div>
       <settings-main id="main" prefs="{{prefs}}"
           toolbar-spinner-active="{{toolbarSpinnerActive_}}"
           page-visibility="[[pageVisibility_]]"
           show-android-apps="[[showAndroidApps_]]"
           advanced-toggle-expanded="{{advancedOpened_}}">
       </settings-main>
-    </paper-header-panel>
+    </div>
   </template>
   <script src="settings_ui.js"></script>
 </dom-module>