Enable download home by default

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

 // 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.
 
 package org.chromium.chrome.browser.download;
 
 import android.app.DownloadManager;
 import android.content.ActivityNotFoundException;
 import android.content.BroadcastReceiver;
 import android.content.Context;
@@ skipping 62 matching lines @@
 
     private static final String TAG = "DownloadService";
     private static final String DOWNLOAD_DIRECTORY = "Download";
     protected static final String PENDING_OMA_DOWNLOADS = "PendingOMADownloads";
     private static final String UNKNOWN_MIME_TYPE = "application/unknown";
     private static final String DOWNLOAD_UMA_ENTRY = "DownloadUmaEntry";
     private static final long UPDATE_DELAY_MILLIS = 1000;
     // Wait 10 seconds to resume all downloads, so that we won't impact tab loading.
     private static final long RESUME_DELAY_MILLIS = 10000;
     private static final int UNKNOWN_DOWNLOAD_STATUS = -1;
+    private static final String PREF_IS_DOWNLOAD_HOME_ENABLED =
+            "org.chromium.chrome.browser.download.IS_DOWNLOAD_HOME_ENABLED";
 
     // Values for the histogram MobileDownloadResumptionCount.
     private static final int UMA_DOWNLOAD_RESUMPTION_MANUAL_PAUSE = 0;
     private static final int UMA_DOWNLOAD_RESUMPTION_BROWSER_KILLED = 1;
     private static final int UMA_DOWNLOAD_RESUMPTION_CLICKED = 2;
     private static final int UMA_DOWNLOAD_RESUMPTION_FAILED = 3;
     private static final int UMA_DOWNLOAD_RESUMPTION_AUTO_STARTED = 4;
     private static final int UMA_DOWNLOAD_RESUMPTION_COUNT = 5;
 
     // Set will be more expensive to initialize, so use an ArrayList here.
@@ skipping 142 matching lines @@
         return prev;
     }
 
     @VisibleForTesting
     protected DownloadManagerService(Context context,
             DownloadNotifier downloadNotifier,
             Handler handler,
             long updateDelayInMillis) {
         mContext = context;
         mSharedPrefs = ContextUtils.getAppSharedPreferences();
+        // Clean up unused shared prefs. TODO(qinmin): remove this after M61.
+        mSharedPrefs.edit().remove(PREF_IS_DOWNLOAD_HOME_ENABLED).apply();
         mDownloadNotifier = downloadNotifier;
         mUpdateDelayInMillis = updateDelayInMillis;
         mHandler = handler;
         mOMADownloadHandler = new OMADownloadHandler(context);
         mDownloadSnackbarController = new DownloadSnackbarController(context);
         mDownloadManagerDelegate = new DownloadManagerDelegate(mContext);
         // Note that this technically leaks the native object, however, DownloadManagerService
         // is a singleton that lives forever and there's no clean shutdown of Chrome on Android.
         init();
         clearPendingOMADownloads();
@@ skipping 1442 matching lines @@
             boolean isNotificationDismissed);
     private native void nativePauseDownload(long nativeDownloadManagerService, String downloadGuid,
             boolean isOffTheRecord);
     private native void nativeRemoveDownload(long nativeDownloadManagerService, String downloadGuid,
             boolean isOffTheRecord);
     private native void nativeGetAllDownloads(
             long nativeDownloadManagerService, boolean isOffTheRecord);
     private native void nativeCheckForExternallyRemovedDownloads(
             long nativeDownloadManagerService, boolean isOffTheRecord);
 }