Wrap legacy WebRTC API in runtime flag

Wrap legacy WebRTC API in runtime flag
https://bugs.webkit.org/show_bug.cgi?id=169646

Patch by Youenn Fablet <youenn@apple.com> on 2017-03-16
Reviewed by Alex Christensen.

Source/WebCore:

Test: webrtc/legacy-api.html

Adding a runtime flag for legacy API.
Making some WebIDL peer connection members runtime-enabled.
Adding a JS private getter on this flag so that overloaded operations behave as promise-based only if flag is turned off.

* Modules/mediastream/RTCPeerConnection.idl:
* Modules/mediastream/RTCPeerConnectionInternals.js:
* bindings/js/JSDOMGlobalObject.cpp:
(WebCore::isWebRTCLegacyAPIEnabled):
(WebCore::JSDOMGlobalObject::addBuiltinGlobals):
* bindings/js/WebCoreBuiltinNames.h:
* page/RuntimeEnabledFeatures.h:
(WebCore::RuntimeEnabledFeatures::webRTCLegacyAPIEnabled):
(WebCore::RuntimeEnabledFeatures::setWebRTCLegacyAPIEnabled):

Source/WebKit/mac:

* WebView/WebPreferenceKeysPrivate.h:
* WebView/WebPreferences.mm:
(+[WebPreferences initialize]):
(-[WebPreferences webRTCLegacyAPIEnabled]):
(-[WebPreferences setWebRTCLegacyAPIEnabled:]):
* WebView/WebPreferencesPrivate.h:
* WebView/WebView.mm:
(-[WebView _preferencesChanged:]):

Source/WebKit2:

Adding preference to legacy API.

* Shared/WebPreferencesDefinitions.h:
* UIProcess/API/C/WKPreferences.cpp:
(WKPreferencesSetWebRTCLegacyAPIEnabled):
(WKPreferencesGetWebRTCLegacyAPIEnabled):
* UIProcess/API/C/WKPreferencesRef.h:
* WebProcess/InjectedBundle/InjectedBundle.cpp:
(WebKit::InjectedBundle::overrideBoolPreferenceForTestRunner):
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::updatePreferences):

Tools:

* DumpRenderTree/mac/DumpRenderTree.mm:
(enableExperimentalFeatures):
* WebKitTestRunner/InjectedBundle/Bindings/TestRunner.idl:
* WebKitTestRunner/InjectedBundle/InjectedBundle.cpp:
(WTR::InjectedBundle::beginTesting):
* WebKitTestRunner/InjectedBundle/TestRunner.cpp:
(WTR::TestRunner::setWebRTCLegacyAPIEnabled):
* WebKitTestRunner/InjectedBundle/TestRunner.h:

LayoutTests:

* webrtc/legacy-api-expected.txt: Added.
* webrtc/legacy-api.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@214080 268f45cc-cd09-0410-ab3c-d52691b4dbfc