Introduce Stream::flush [2/2 chromium]
There is no way to flush the buffer in the stream.
This cl introduces Stream::flush method.
We can flush the buffer in the browser process using this method from blink.
We will use this method when we send the data from the ServiceWorker to the browser process progressively.
blink: https://codereview.chromium.org/747323007/
2/2 chromium: https://codereview.chromium.org/
760823002/
BUG=436424
Review URL: https://codereview.chromium.org/
760823002
Cr-Commit-Position: refs/heads/master@{#307684}