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In the existing code, for Drive FS path,
ConvertPathToArcUrl() will call guest_os::GuestOsSharePath::SharePath(),
which in turns will call Seneschal's SharePath(). As Seneschal's
SharePath() is an asynchronous call, it may result in a race condition.

To solve this:
1. ConvertPathToArcUrl() will return a flag to indicate if the path
needs to be shared.
2. ConvertToContentUrls() will return a list of paths to be shared.
3. A new wrapper function ConvertToContentUrlsAndShare() will handle
the path sharing after path conversion is completed.

Bug: b:161427985
Test:
1. With FilesApp's OpenWith function (in ARC++/ARCVM), android app can open
a Drive FS file.
2. Intent URI can launch an android app.
3. Chrome OS FilesApp as Android file picker works.
4. Drag-and-drop Drive FS file to an android app can open the file.
5. Drive FS thumbnails are showing properly.
6. Chrome camera app can open/save file normally.
7. Note taking android app can annotate images.

Change-Id: Idfb0069b7ad2b407cf599748b766b4bf4899b7bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601007Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Nancy Wang <nancylingwang@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Cherie Cheung <cherieccy@google.com>
Cr-Commit-Position: refs/heads/master@{#844149}