[CoordinatedGraphics] Use ScrollingStateTree to handle fixed elements positioning while scrolling
https://bugs.webkit.org/show_bug.cgi?id=114353

Reviewed by Noam Rosenthal.

ScrollingCoordinatorCoordinatedGraphics should implement threaded scrolling interface and
re-use threaded scrolling approach (ScrollingStateTree and ViewportConstraints) to handle
fixed/sticky elements positioning while scrolling. The rationals are below.

Before the change ScrollingCoordinatorCoordinatedGraphics was implementing Chromium-specific
interface which is going to be removed eventually as there is no ScrollingCoordinatorChromium
existing.

Tested by existing manual tests (fixed-position.html for example.

* CMakeLists.txt:
* Target.pri:
    Included ScrollingStateTree files.

* page/scrolling/ScrollingStateFixedNode.cpp:
* page/scrolling/ScrollingStateFixedNode.h:
* page/scrolling/ScrollingStateNode.cpp:
* page/scrolling/ScrollingStateNode.h:
* page/scrolling/ScrollingStateScrollingNode.cpp:
* page/scrolling/ScrollingStateScrollingNode.h:
* page/scrolling/ScrollingStateStickyNode.cpp:
* page/scrolling/ScrollingStateStickyNode.h:
* page/scrolling/ScrollingStateTree.cpp:
* page/scrolling/ScrollingStateTree.h:
    Removed ENABLE(THREADED_SCROLLING) code guards.

* page/scrolling/coordinatedgraphics/ScrollingCoordinatorCoordinatedGraphics.cpp:
(WebCore::ScrollingCoordinatorCoordinatedGraphics::ScrollingCoordinatorCoordinatedGraphics):
(WebCore::ScrollingCoordinatorCoordinatedGraphics::~ScrollingCoordinatorCoordinatedGraphics):
(WebCore):
(WebCore::ScrollingCoordinatorCoordinatedGraphics::attachToStateTree):
(WebCore::ScrollingCoordinatorCoordinatedGraphics::detachFromStateTree):
(WebCore::ScrollingCoordinatorCoordinatedGraphics::clearStateTree):
(WebCore::ScrollingCoordinatorCoordinatedGraphics::updateViewportConstrainedNode):
* page/scrolling/coordinatedgraphics/ScrollingCoordinatorCoordinatedGraphics.h:
    ScrollingCoordinatorCoordinatedGraphics is using threaded scrolling approach to handle fixed
    elements positioning while scrolling.

(WebCore):
(ScrollingCoordinatorCoordinatedGraphics):
* page/scrolling/coordinatedgraphics/ScrollingStateNodeCoordinatedGraphics.cpp: Added.
(WebCore):
(WebCore::ScrollingStateNode::platformScrollLayer):
(WebCore::ScrollingStateNode::setScrollPlatformLayer):
(WebCore::ScrollingStateNode::setScrollLayer):
* page/scrolling/coordinatedgraphics/ScrollingStateScrollingNodeCoordinatedGraphics.cpp: Added.
(WebCore):
(WebCore::ScrollingStateScrollingNode::counterScrollingPlatformLayer):
(WebCore::ScrollingStateScrollingNode::setCounterScrollingLayer):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148197 268f45cc-cd09-0410-ab3c-d52691b4dbfc