foolip@ notes that init segment used to generate the network error doesn't need to be encoded in JavaScript and can be a file instead retrieved via XHR if we make the test a wpt test.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d66554b28a0a09e3a96eb4554eb35ece58a3327f

commit d66554b28a0a09e3a96eb4554eb35ece58a3327f
Author: Dale Curtis <dalecurtis@chromium.org>
Date: Wed May 09 19:44:33 2018

Remove Internals::setMediaElementNetworkState(); always trouble.

ClusterFuzz routinely uses this to create fake bugs and there's only
three tests which use this:
- controls-repaint-for-network-change.html, which is a broken test and
tests nothing (i.e. breaking it still passes)
- media-play-promise.html #playDecodeError, which doesn't need to; it
can just use a real corrupt file.
- media-play-promise.html #playNetworkError, which is also a broken
test and with the addition of a true test reveals that the underlying
behavior being tested is underspecified. Filed http://crbug.com/841063

Code has been added to test network errors via MSEs ability to force a
network error on EOS, but as mentioned the underlying behavior being
tested by the test is broken. For now the test is commented out.

BUG= 839288 , 841063
TEST=existing tests pass.

Change-Id: I0c48f305d24760c6bace7113297423b44e93728b
Reviewed-on: https://chromium-review.googlesource.com/1043493
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557284}
[delete] https://crrev.com/8aa1e54c131a3117043ea16af89340f99497c6ec/third_party/WebKit/LayoutTests/media/controls-repaint-for-network-change-expected.html
[delete] https://crrev.com/8aa1e54c131a3117043ea16af89340f99497c6ec/third_party/WebKit/LayoutTests/media/controls-repaint-for-network-change.html
[modify] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/WebKit/LayoutTests/media/media-play-promise-expected.txt
[modify] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/WebKit/LayoutTests/media/media-play-promise.html
[add] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/WebKit/LayoutTests/media/network-error.js
[modify] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/blink/renderer/core/testing/internals.cc
[modify] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/blink/renderer/core/testing/internals.h
[modify] https://crrev.com/d66554b28a0a09e3a96eb4554eb35ece58a3327f/third_party/blink/renderer/core/testing/internals.idl