<style scoped>: Add runtime-flag

<style scoped>: Add runtime-flag
https://bugs.webkit.org/show_bug.cgi?id=79074

Source/WebCore:

Added runtime-flag.
Query runtime flag when (un)registering a <style scoped> element, and when determineing a style sheet's scope.

Reviewed by Dimitri Glazkov.

No new tests. (no change in functionality)

* bindings/generic/RuntimeEnabledFeatures.cpp:
(WebCore):
* bindings/generic/RuntimeEnabledFeatures.h:
(RuntimeEnabledFeatures):
(WebCore::RuntimeEnabledFeatures::styleScopedEnabled):
(WebCore::RuntimeEnabledFeatures::setStyleScopedEnabled):
* css/CSSStyleSelector.cpp:
(WebCore::CSSStyleSelector::determineScopingElement):
* html/HTMLStyleElement.cpp:
(WebCore::HTMLStyleElement::registerWithScopingNode):
(WebCore::HTMLStyleElement::unregisterWithScopingNode):
* html/HTMLStyleElement.idl:

Source/WebKit/chromium:

Added a runtime-flag.
Enable default STYLE_SCOPED compile-time flag for Chromium.

Reviewed by Dimitri Glazkov.

* features.gypi: enable STYLE_SCOPED
* public/WebRuntimeFeatures.h:
(WebRuntimeFeatures):
* src/WebRuntimeFeatures.cpp:
(WebKit::WebRuntimeFeatures::enableStyleScoped):
(WebKit):
(WebKit::WebRuntimeFeatures::isStyleScopedEnabled):

Tools:

Enable the runtime-flag for DRT.

Reviewed by Dimitri Glazkov.

* DumpRenderTree/chromium/TestShell.cpp:
(TestShell::TestShell):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108474 268f45cc-cd09-0410-ab3c-d52691b4dbfc