Make DataOffer::SetDropData handle filesystem:// URLs.

Below are the steps for converting Chrome-specific filesystem:// URLs into ARC URLs.
1) Extract filesystem URL(s) from pickle.
  -> "filesystem:chrome-extension://hhao.../external/drive-.../root/...."
2) Crack URL with FileSystemContext.
  -> "/special/drive-.../root/...."
3) Convert to Arc URL
  -> "content://org.chromium.arc.chromecontentprovider/externalfile%3Adrive-.../root/...."

Bug: chromium:767982
Test: out/Default/exo_unittests --gtest_filter="DataOffer.*"
Change-Id: I9fc803f69acd0d3573c25668ca5786d7e6002501
Reviewed-on: https://chromium-review.googlesource.com/867807
Commit-Queue: Satoshi Niwa <[email protected]>
Reviewed-by: David Reveman <[email protected]>
Reviewed-by: Ryo Hashimoto <[email protected]>
Cr-Commit-Position: refs/heads/master@{#532756}
6 files changed