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* Adds hooks in DownloadManagerService for calling GetAllDownloads()
  and sending the information back to Java.  This creates a
  List of DownloadItems that contain the basic information needed
  for the UI.

* Adds a basic RecyclerView to display the files in the user's
  download history.

* Adds a DownloadHistoryAdapter that is used to track information
  about the download history.  This *should* be reusable among
  multiple RecyclerViews in case the user opens up multi-window
  mode.

- This currently doesn't monitor any changes to the history and is
  used solely for getting a skeleton working.

BUG=616324

Review-Url: https://codereview.chromium.org/2143303002
Cr-Commit-Position: refs/heads/master@{#405607}