https://bugs.webkit.org/show_bug.cgi?id=135506

Patch by Benjamin Poulain <bpoulain@apple.com> on 2014-08-28
Reviewed by Simon Fraser.

Source/WebCore:

When scrolling by page, find the height of any bar that is obscuring the top or bottom of the page,
and substract that height from the step to scroll.

Tests: scrollbars/scrolling-backward-by-page-accounting-bottom-fixed-elements-on-keyboard-spacebar.html
       scrollbars/scrolling-backward-by-page-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-accounting-oversized-fixed-elements-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-accounting-top-fixed-elements-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-accounting-top-fixed-elements-with-negative-top-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-ignoring-hidden-fixed-elements-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-ignoring-transparent-fixed-elements-on-keyboard-spacebar.html
       scrollbars/scrolling-by-page-on-keyboard-spacebar.html

* WebCore.exp.in:
* page/FrameView.cpp:
(WebCore::FrameView::adjustScrollStepForFixedContent):
* page/FrameView.h:
* platform/ScrollableArea.cpp:
(WebCore::ScrollableArea::adjustScrollStepForFixedContent):
(WebCore::ScrollableArea::scroll):
* platform/ScrollableArea.h:

LayoutTests:

There was pretty much no test coverage for scrolling by page, add some tests.

* fast/events/scrollbar-double-click-expected.txt:
* platform/mac-wk1/TestExpectations:
* scrollbars/scrolling-backward-by-page-accounting-bottom-fixed-elements-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-backward-by-page-accounting-bottom-fixed-elements-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-backward-by-page-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-backward-by-page-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-accounting-oversized-fixed-elements-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-accounting-oversized-fixed-elements-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-accounting-top-fixed-elements-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-accounting-top-fixed-elements-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-accounting-top-fixed-elements-with-negative-top-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-accounting-top-fixed-elements-with-negative-top-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-ignoring-hidden-fixed-elements-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-ignoring-hidden-fixed-elements-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-ignoring-transparent-fixed-elements-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-ignoring-transparent-fixed-elements-on-keyboard-spacebar.html: Added.
* scrollbars/scrolling-by-page-on-keyboard-spacebar-expected.txt: Added.
* scrollbars/scrolling-by-page-on-keyboard-spacebar.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@173074 268f45cc-cd09-0410-ab3c-d52691b4dbfc