Fix duplicate space calculation on Android download home.

chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java

Index: chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java b/chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java
index bca450bbd0b7fdbd4e8e3269deb4d66c995722f4..6ceb6f546bb7588c6a3ebeb8014c2b3c50c75e2b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/ui/BackendItems.java
@@ -9,6 +9,7 @@ import android.text.TextUtils;
 import org.chromium.chrome.browser.widget.DateDividedAdapter.TimedItem;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 
@@ -28,8 +29,13 @@ public abstract class BackendItems extends ArrayList<DownloadHistoryItemWrapper>
      */
     public long getTotalBytes() {
         long totalSize = 0;
+        HashSet<String> filePaths = new HashSet<>();
         for (DownloadHistoryItemWrapper item : this) {
-            if (item.isVisibleToUser(DownloadFilter.FILTER_ALL)) totalSize += item.getFileSize();
+            String path = item.getFilePath();
+            if (item.isVisibleToUser(DownloadFilter.FILTER_ALL) && !filePaths.contains(path)) {
+                totalSize += item.getFileSize();
+            }
+            if (!path.isEmpty()) filePaths.add(path);
         }
         return totalSize;
     }