FindBanner matches are offset when the WKView has a header or footer
https://bugs.webkit.org/show_bug.cgi?id=114314
-and corresponding-
<rdar://problem/13522434>

Reviewed by Simon Fraser.

Source/WebCore: 

There were already a few places in the code where we needed to adjust the 
scrollOffset() to pretend that (0,0) is that the top of the Document rather than 
the top of the header. To fix the FindBanner issues, we need to know that version 
of the offset in a few more places, so I added a function on ScrollView to fetch 
it called scrollOffsetRelativeToDocument().

New function subtracts out the headerHeight() to treat the top of 
the document as (0,0).
* WebCore.exp.in:
* platform/ScrollView.cpp:
(WebCore::ScrollView::scrollOffsetRelativeToDocument):

Use scrollOffsetRelativeToDocument() where we were previously making this 
calculation. Also re-name an inaccurately named variable where we are actually 
converting FROM a document offset to a ScrollableArea offset.
(WebCore::ScrollView::windowToContents):
* platform/ScrollView.h:
(ScrollView):

getRectToExpose needs to know about the actual visibleContentRect and the 
visibleContentRect that is relative to the Document. So this 
patch adds a new parameter to getRectToExpose for that purpose.
* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::scrollRectToVisible):
(WebCore::RenderLayer::getRectToExpose):
* rendering/RenderLayer.h:

Source/WebKit2: 

When calculating the matching rects, also adjust to the scroll offset that is  
relative to the Document.
* WebProcess/WebPage/FindController.cpp:
(WebKit::FindController::rectsForTextMatches):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148137 268f45cc-cd09-0410-ab3c-d52691b4dbfc