Fix repositioning of fixed elements on zooming

Fix repositioning of fixed elements on zooming
https://bugs.webkit.org/show_bug.cgi?id=105223

Reviewed by Beth Dakin.

Source/WebCore:

When zoomed, scrolling would move the layers of fixed-position
elements oddly. This happened because on the scrolling thread we
passed a scale of 1, rather than the actual page scale to
scrollOffsetForFixedPosition().

Fix by plumbing the page scale through the scrolling state node
to the scrolling node.

Test: platform/mac/tiled-drawing/fixed/four-bars-zoomed.html

* page/scrolling/ScrollingStateScrollingNode.cpp:
(WebCore::ScrollingStateScrollingNode::ScrollingStateScrollingNode):
(WebCore::ScrollingStateScrollingNode::setFrameScaleFactor):
(WebCore::ScrollingStateScrollingNode::dumpProperties):
* page/scrolling/ScrollingStateScrollingNode.h:
(WebCore::ScrollingStateScrollingNode::frameScaleFactor):
(ScrollingStateScrollingNode):
* page/scrolling/ScrollingTreeScrollingNode.cpp:
(WebCore::ScrollingTreeScrollingNode::ScrollingTreeScrollingNode):
(WebCore::ScrollingTreeScrollingNode::update):
* page/scrolling/ScrollingTreeScrollingNode.h:
(WebCore::ScrollingTreeScrollingNode::frameScaleFactor):
(ScrollingTreeScrollingNode):
* page/scrolling/mac/ScrollingCoordinatorMac.h:
(ScrollParameters):
* page/scrolling/mac/ScrollingCoordinatorMac.mm:
(WebCore::ScrollingCoordinatorMac::frameViewLayoutUpdated):
(WebCore::ScrollingCoordinatorMac::setScrollParametersForNode):
* page/scrolling/mac/ScrollingTreeScrollingNodeMac.mm:
(WebCore::ScrollingTreeScrollingNodeMac::setScrollLayerPosition):

LayoutTests:

Testcase that zoomed with fixed-position elements.

* platform/mac/tiled-drawing/fixed/four-bars-zoomed-expected.txt: Added.
* platform/mac/tiled-drawing/fixed/four-bars-zoomed.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@137957 268f45cc-cd09-0410-ab3c-d52691b4dbfc