Convert src/core/chunked_stream.js to ES6 syntax

[timvandermeij]

While we're here, remove the unused url argument for the ChunkedStreamManager class that I found during the refactoring.

@Snuffleupagus Would you be willing to review this? I found that GitHub can't apply the ?w=1 flag for the first commit for some reason, so here is the output of git show -w HEAD~1: https://dpaste.de/vUQU

[timvandermeij]

/botio-linux preview

[timvandermeij]

/botio test

[Snuffleupagus]

Looks generally good, thank you; but setting r- for the skip method alone.

[timvandermeij]

/botio-linux preview

[pdfjsbot]

From: Bot.io (Linux m4)

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Received

Command cmd_preview from @timvandermeij received. Current queue size: 0

Live output at: http://54.67.70.0:8877/2b7dbc9841d1b0b/output.txt

[pdfjsbot]

From: Bot.io (Linux m4)

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Success

Full output at http://54.67.70.0:8877/2b7dbc9841d1b0b/output.txt

Total script time: 1.66 mins

Published

• Viewer: http://54.67.70.0:8877/2b7dbc9841d1b0b/web/viewer.html

[timvandermeij]

/botio test

[pdfjsbot]

From: Bot.io (Linux m4)

---

Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://54.67.70.0:8877/8f8cb896fa67864/output.txt

[pdfjsbot]

From: Bot.io (Windows)

---

Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://54.215.176.217:8877/9181b1c2466c83a/output.txt

[pdfjsbot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.67.70.0:8877/8f8cb896fa67864/output.txt

Total script time: 17.66 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed

[pdfjsbot]

From: Bot.io (Windows)

---

Success

Full output at http://54.215.176.217:8877/9181b1c2466c83a/output.txt

Total script time: 23.35 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed