[Downloads] Expose basic download history to UI

chrome/android/java/res/layout/download_main.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2016 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. -->
 
 <org.chromium.chrome.browser.download.ui.DownloadManagerUi
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent" >
 
     <!-- MAIN CONTENT -->
-    <RelativeLayout
+    <LinearLayout
         android:id="@+id/content_frame"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:background="#ffffff">
+        android:background="#ffffff"
+        android:orientation="vertical" >
         
         <org.chromium.chrome.browser.download.ui.DownloadManagerToolbar
             android:id="@id/action_bar"
             android:layout_width="match_parent"
             android:layout_height="?attr/actionBarSize"
-            android:layout_alignParentTop="true"
-            android:layout_alignParentStart="true"
-            android:layout_alignParentEnd="true"
-            android:background="@color/appbar_background" >
-        </org.chromium.chrome.browser.download.ui.DownloadManagerToolbar>
-    
+            android:background="@color/appbar_background" />
+
         <org.chromium.chrome.browser.widget.FadingShadowView
             android:id="@+id/shadow"
             android:layout_width="match_parent"
             android:layout_height="10dp"
-            android:layout_below="@id/action_bar" />
+            android:layout_marginBottom="-10dp" />
+    
+        <android.support.v7.widget.RecyclerView
+            android:id="@+id/recycler_view"
+            android:layout_width="match_parent"
+            android:layout_height="0dp"
+            android:layout_weight="1" />
 
-        <!-- Insert RecyclerView here for showing items (or lack thereof). -->
-    </RelativeLayout>
+    </LinearLayout>
 
     <!-- NAVIGATION DRAWER
          We can't assign a paddingStart or paddingEnd because the section highlights are full-bleed.
     -->
     <LinearLayout
         android:id="@+id/drawer_layout"
         android:layout_width="@dimen/drawer_width"
         android:layout_height="match_parent"
         android:layout_gravity="start"
         android:paddingTop="@dimen/drawer_margin_large"
         android:orientation="vertical"
         android:background="#ffffff" >
 
         <include layout="@layout/download_manager_ui_space_widget"/>
 
         <ListView
             android:id="@+id/section_list"
             android:layout_width="match_parent"
             android:layout_height="0dp"
             android:layout_weight="1"
             android:divider="@null"
             android:dividerHeight="0dp" />
     </LinearLayout>
 
 </org.chromium.chrome.browser.download.ui.DownloadManagerUi>