Delete download in Android DownloadManager when download is deleted from download home

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

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerDelegate.java
index 3e5221e5f0a190ce2e5fb0f4b5e6f70dc23ecdeb..d7e274e3d01eff3411d46bfbb9e337fee13bfb87 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerDelegate.java
@@ -6,12 +6,14 @@ package org.chromium.chrome.browser.download;
 
 import android.app.DownloadManager;
 import android.content.Context;
+import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Build;
 import android.support.v4.app.NotificationManagerCompat;
 
+import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 
 import java.lang.reflect.InvocationTargetException;
@@ -22,6 +24,8 @@ import java.lang.reflect.Method;
  */
 public class DownloadManagerDelegate {
     private static final String TAG = "DownloadDelegate";
+    private static final long INVALID_SYSTEM_DOWNLOAD_ID = -1;
+    private static final String DOWNLOAD_ID_MAPPINGS_FILE_NAME = "download_id_mappings";
     protected final Context mContext;
 
     public DownloadManagerDelegate(Context context) {
@@ -29,15 +33,55 @@ public class DownloadManagerDelegate {
     }
 
     /**
+     * Inserts a new download ID mapping into the SharedPreferences
+     * @param downloadId system download ID from Android DownloadManager.
+     * @param downloadGuid Download GUID.
+     */
+    private void addDownloadIdMapping(long downloadId, String downloadGuid) {
+        SharedPreferences sharedPrefs = getSharedPreferences();
+        SharedPreferences.Editor editor = sharedPrefs.edit();
+        editor.putLong(downloadGuid, downloadId);
+        editor.apply();
+    }
+
+    /**
+     * Removes a download Id mapping from the SharedPreferences given the download GUID.
+     * @param guid Download GUID.
+     * @return the Android DownloadManager's download ID that is removed, or
+     *         INVALID_SYSTEM_DOWNLOAD_ID if it is not found.
+     */
+    private long removeDownloadIdMapping(String downloadGuid) {
+        SharedPreferences sharedPrefs = getSharedPreferences();
+        long downloadId = sharedPrefs.getLong(downloadGuid, INVALID_SYSTEM_DOWNLOAD_ID);
+        if (downloadId != INVALID_SYSTEM_DOWNLOAD_ID) {
+            SharedPreferences.Editor editor = sharedPrefs.edit();
+            editor.remove(downloadGuid);
+            editor.apply();
+        }
+        return downloadId;
+    }
+
+    /**
+     * Lazily retrieve the SharedPreferences when needed. Since download operations are not very
+     * frequent, no need to load all SharedPreference entries into a hashmap in the memory.
+     * @return the SharedPreferences instance.
+     */
+    private SharedPreferences getSharedPreferences() {
+        return ContextUtils.getApplicationContext().getSharedPreferences(
+                DOWNLOAD_ID_MAPPINGS_FILE_NAME, Context.MODE_PRIVATE);
+    }
+
+    /**
      * @see android.app.DownloadManager#addCompletedDownload(String, String, boolean, String,
      * String, long, boolean)
      */
     protected long addCompletedDownload(String fileName, String description, String mimeType,
-            String path, long length, String originalUrl, String referer) {
+            String path, long length, String originalUrl, String referer, String downloadGuid) {
         DownloadManager manager =
                 (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);
         NotificationManagerCompat notificationManager = NotificationManagerCompat.from(mContext);
         boolean useSystemNotification = !notificationManager.areNotificationsEnabled();
+        long downloadId = -1;
         if (Build.VERSION.SDK_INT > Build.VERSION_CODES.M) {
             Class<?> c = manager.getClass();
             try {
@@ -46,8 +90,8 @@ public class DownloadManagerDelegate {
                 Method method = c.getMethod("addCompletedDownload", args);
                 Uri originalUri = Uri.parse(originalUrl);
                 Uri refererUri = referer == null ? Uri.EMPTY : Uri.parse(referer);
-                return (Long) method.invoke(manager, fileName, description, true, mimeType, path,
-                        length, useSystemNotification, originalUri, refererUri);
+                downloadId = (Long) method.invoke(manager, fileName, description, true, mimeType,
+                        path, length, useSystemNotification, originalUri, refererUri);
             } catch (SecurityException e) {
                 Log.e(TAG, "Cannot access the needed method.");
             } catch (NoSuchMethodException e) {
@@ -58,8 +102,23 @@ public class DownloadManagerDelegate {
                 Log.e(TAG, "Error accessing the needed method.");
             }
         }
-        return manager.addCompletedDownload(fileName, description, true, mimeType, path, length,
-                useSystemNotification);
+        downloadId = manager.addCompletedDownload(fileName, description, true, mimeType, path,
+                length, useSystemNotification);
+        addDownloadIdMapping(downloadId, downloadGuid);
+        return downloadId;
+    }
+
+    /**
+     * Removes a download from Android DownloadManager.
+     * @param downloadGuid The GUID of the download.
+     */
+    void removeCompletedDownload(String downloadGuid) {
+        long downloadId = removeDownloadIdMapping(downloadGuid);
+        if (downloadId != INVALID_SYSTEM_DOWNLOAD_ID) {
+            DownloadManager manager =
+                    (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);
+            manager.remove(downloadId);
+        }
     }
 
     /**