FileAPI: Add three new Blob APIs

This change adds the implementation for three new Blob APIs: stream(),
text(), and arrayBuffer().

Related web platform tests: https://crrev.com/c/1526796/

Spec: https://www.w3.org/TR/FileAPI/
Bug: 945893
Change-Id: Ieb06be0e9023685a12eaa79bd77d69cb13fa5412
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529716
Commit-Queue: Jarryd Goodman <jarrydg@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652912}
11 files changed