Change Observer: Add WPTs for writable file streams
Adds expectations for all writable file stream methods.
Test failure expectations are added for closed events reporting as
"appeared" instead of "modified" due to bug 340584120.
Bug: 341136316
Change-Id: Id01f9ab849437793a6d69b7281aea394c03c76c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5743270
Commit-Queue: Nathan Memmott memmott@chromium.org
Reviewed-by: Daseul Lee dslee@chromium.org
Cr-Commit-Position: refs/heads/main@{#1334934}