Misc minor changes in WebSockets tests.

This CL partially re-lands https://crrev.com/c/927491 among other
things.  This CL is mostly to prepare for adding tests for WebSockets
over HTTP/2.

Add missing include to spdy_network_transaction_unittest.cc for
HttpResponseInfo.

Change two WebSockets test file to use wildcard.pem instead of
spdy_pooling.pem.

Move WebSocketExtraHeadersToString from a test file anonymous namespace
to websocket_test_utils.h.  Also change argument type for extra headers
in websocket_stream_test.cc to WebSocketExtraHeaders and use this helper
function to convert them to a string.

In websocket_stream_test.cc:
* Change all tests to use www.example.org instead of localhost so that
  it is compatible with the test certificate wildcard.pem.  (This is
  only a requirement for wss, but it is cleaner if all tests use the
  same hostname.)
* Change tests that will be parametrized to test WebSockets over HTTP/2
  as well to use wss scheme.
* Change WebSocketStreamCreateUMATest to be a derived class of
  WebSocketStreamCreateTest instead of creating an instance of it, and
  use HistogramTester for simplicity.
* Change test base class methods and members from public to protected.
* Inline trivial AddRawExpectations() method.

Bug: 801564
Change-Id: I76a3ed145baa0f9171089765852e3165d43c9710
Reviewed-on: https://chromium-review.googlesource.com/942522
Commit-Queue: Bence Béky <bnc@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540509}
6 files changed