Download Home v2: Fix a crash when resuming download.

The download guid in DownloadInfo.java is not plumbed from OfflineItem.
This will cause DownloadItem.getId() or DownloadInfo.getDownloadGuid()
to return null.

Bug: 889369
Change-Id: I73fc66e16d2fa3b6e7a0e8d02dff9655f259f7d1
Reviewed-on: https://chromium-review.googlesource.com/1249835Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594863}

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

@@ -248,6 +248,7 @@ public final class DownloadInfo {
 
         return new DownloadInfo.Builder()
                 .setContentId(item.id)
+                .setDownloadGuid(item.id.id)
                 .setFileName(item.title)
                 .setFilePath(item.filePath)
                 .setDescription(item.description)