Add a test for swipe-start hysteresis

Add a test for swipe-start hysteresis
https://bugs.webkit.org/show_bug.cgi?id=148756

Reviewed by Anders Carlsson.

* swipe/basic-cached-back-swipe.html:
* swipe/pushState-cached-back-swipe.html:
* swipe/resources/swipe-test.js:
(testComplete):
* swipe/swipe-start-hysteresis-failures.html: Added.
* swipe/swipe-start-hysteresis-failures-expected.txt: Added.

* WebKitTestRunner/InjectedBundle/Bindings/TestRunner.idl:
* WebKitTestRunner/InjectedBundle/TestRunner.cpp:
(WTR::cacheTestRunnerCallback):
(WTR::TestRunner::clearTestRunnerCallbacks):
* WebKitTestRunner/InjectedBundle/TestRunner.h:
Make sure that we log if a client tries to install a callback twice
(since we use .add, the second call would not work).

Also, add clearTestRunnerCallbacks so tests can swap out installed
callbacks.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@189321 268f45cc-cd09-0410-ab3c-d52691b4dbfc