Move RenderLayer::scrolledContentOffset calls to a common function

Move RenderLayer::scrolledContentOffset calls to a common function
https://bugs.webkit.org/show_bug.cgi?id=76971

Reviewed by David Hyatt.

Refactoring without any change in behavior.

This change adds a RenderBox::scrolledContentOffset function to handle all
the calls that goes through the layer(). This indirection will enable us to
add layer() checks without patching a lot of call sites as part of bug 75568.

We also moved down the concept of scroll offset down to RenderBox where it belongs!

* rendering/RenderLayer.h:
(RenderLayer):
(WebCore::RenderLayer::scrolledContentOffset):
Moved scrolledContent to the private section of the class to prevent misuse.

* rendering/RenderBox.cpp:
(WebCore::RenderBox::scrolledContentOffset):
New function to add an indirection with RenderLayer.

* editing/visible_units.cpp:
(WebCore::absoluteLineDirectionPointToLocalPointInBlock):
* rendering/LayoutState.cpp:
(WebCore::LayoutState::LayoutState):
* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::layoutBlock):
(WebCore::RenderBlock::paintObject):
(WebCore::RenderBlock::selectionGapRectsForRepaint):
(WebCore::RenderBlock::paintSelection):
(WebCore::RenderBlock::nodeAtPoint):
(WebCore::RenderBlock::offsetForContents):
* rendering/RenderBox.cpp:
(WebCore::RenderBox::offsetFromContainer):
(WebCore::RenderBox::computeRectForRepaint):
* rendering/RenderBox.h:
(RenderBox):
* rendering/RenderBoxModelObject.cpp:
(WebCore::RenderBoxModelObject::paintFillLayerExtended):
* rendering/RenderInline.cpp:
(WebCore::RenderInline::clippedOverflowRectForRepaint):
(WebCore::RenderInline::computeRectForRepaint):
(WebCore::RenderInline::offsetFromContainer):
* rendering/RenderObject.cpp:
(WebCore::RenderObject::computeRectForRepaint):
(WebCore::RenderObject::mapLocalToContainer):
(WebCore::RenderObject::mapAbsoluteToLocalPoint):
(WebCore::RenderObject::offsetFromContainer):
* rendering/RenderTextControlSingleLine.cpp:
(WebCore::RenderTextControlInnerBlock::positionForPoint):
Patched all those call sites to use the new function.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108382 268f45cc-cd09-0410-ab3c-d52691b4dbfc