[GStreamer] Review WebKitWebSource after r219252.

[GStreamer] Review WebKitWebSource after r219252.
https://bugs.webkit.org/show_bug.cgi?id=174415

Patch by Charlie Turner <cturner@igalia.com> on 2017-07-26
Reviewed by Carlos Garcia Campos.

Remove ResourceHandleStreamingClient, and flatten the StreamingClient
into CachedResourceStreamingClient (the only implemetation left). They
are no longer required after r219252.

Also remove the locking code. It's not needed now, and what existed
was heavy-handed and missed several cases it was supposed to protect

Covered by existing tests.

* platform/graphics/gstreamer/WebKitWebSourceGStreamer.cpp:
(webkit_web_src_init):
(webKitWebSrcDispose):
(webKitWebSrcStop):
(webKitWebSrcStart):
(webKitWebSrcNeedData):
(webKitWebSrcEnoughData):
(webKitWebSrcSeek):
(webKitWebSrcSetMediaPlayer):
(CachedResourceStreamingClient::CachedResourceStreamingClient):
(CachedResourceStreamingClient::~CachedResourceStreamingClient):
(CachedResourceStreamingClient::getOrCreateReadBuffer):
(CachedResourceStreamingClient::responseReceived):
(CachedResourceStreamingClient::dataReceived):
(CachedResourceStreamingClient::loadFinished):
(ResourceHandleStreamingClient::create): Deleted.
(): Deleted.
(StreamingClient::StreamingClient): Deleted.
(StreamingClient::~StreamingClient): Deleted.
(StreamingClient::createReadBuffer): Deleted.
(StreamingClient::handleResponseReceived): Deleted.
(StreamingClient::handleDataReceived): Deleted.
(StreamingClient::handleNotifyFinished): Deleted.
(ResourceHandleStreamingClient::ResourceHandleStreamingClient): Deleted.
(ResourceHandleStreamingClient::~ResourceHandleStreamingClient): Deleted.
(ResourceHandleStreamingClient::cleanupAndStopRunLoop): Deleted.
(ResourceHandleStreamingClient::invalidate): Deleted.
(ResourceHandleStreamingClient::loadFailed): Deleted.
(ResourceHandleStreamingClient::setDefersLoading): Deleted.
(ResourceHandleStreamingClient::getOrCreateReadBuffer): Deleted.
(ResourceHandleStreamingClient::willSendRequest): Deleted.
(ResourceHandleStreamingClient::didReceiveResponse): Deleted.
(ResourceHandleStreamingClient::didReceiveData): Deleted.
(ResourceHandleStreamingClient::didReceiveBuffer): Deleted.
(ResourceHandleStreamingClient::didFinishLoading): Deleted.
(ResourceHandleStreamingClient::didFail): Deleted.
(ResourceHandleStreamingClient::wasBlocked): Deleted.
(ResourceHandleStreamingClient::cannotShowURL): Deleted.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@219959 268f45cc-cd09-0410-ab3c-d52691b4dbfc