[FileSystem] Add support for passing ReadableStream to write.

Bug: 872462
Change-Id: I0f20f1c71d3d9aee53a2f875198e1e4b3461d90c
Reviewed-on: https://chromium-review.googlesource.com/1232397
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595711}
18 files changed