Change "client" coordinates back to match scrolling coordinates

Change "client" coordinates back to match scrolling coordinates
https://bugs.webkit.org/show_bug.cgi?id=174734
rdar://problem/33336930

Reviewed by Tim Horton.

Baidu.com (which uses jQuery), and various iOS apps make the assumption that getBoundingClientRect() returns a rectangle
that can be used to set or compare with the scroll position. With visual viewports, that assumption is no longer valid
when the page is zoomed, or when the keyboard has caused the visual viewport to detach from the layout viewport.

At this point the compatibility cost of shipping layout viewport-based client rects seems higher than the gain, so revert
to the shipping behavior. This reverts r216803, and will re-introduce bugs that occurred on zoomed pages on macOS,
many of which are noted in webkit.org/b/170981.

* page/FrameView.cpp:
(WebCore::FrameView::documentToClientOffset):

LayoutTests:
Revert "client" coordinates to be in scrolling coordinates
https://bugs.webkit.org/show_bug.cgi?id=174734
rdar://problem/33336930

Reviewed by Tim Horton.

Rebaseline.

* fast/events/ios/no-touch-events-when-stopping-momentum-scroll-in-mainframe-expected.txt:
* fast/visual-viewport/client-coordinates-relative-to-layout-viewport-expected.txt:
* fast/visual-viewport/client-rects-relative-to-layout-viewport-expected.txt:
* fast/visual-viewport/zoomed-fixed-expected.txt:
* fast/visual-viewport/zoomed-fixed-header-and-footer-expected.txt:
* fast/zooming/client-rect-in-fixed-zoomed-expected.txt:
* platform/ios-wk2/fast/visual-viewport/client-rects-relative-to-layout-viewport-expected.txt:
* platform/ios-wk2/imported/w3c/web-platform-tests/cssom-view/elementFromPoint-expected.txt: Added.
* platform/ios/fast/visual-viewport/zoomed-fixed-expected.txt:
* platform/ios/fast/visual-viewport/zoomed-fixed-header-and-footer-expected.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@219829 268f45cc-cd09-0410-ab3c-d52691b4dbfc