Make AccessibilityObject::size non-virtual and fix platform accessibility code's...

Make AccessibilityObject::size non-virtual and fix platform accessibility code's LayoutUnit usage
https://bugs.webkit.org/show_bug.cgi?id=83803

Reviewed by Eric Seidel.

AccessibilityObject::size was virtual with a number of overloads, but all the implementations were
redundant. Avoiding the virtual thunk and code duplication by declaring it non-virtual and only
implementing it in AccessibilityObject.

Also adding a pixelSnappedSize method that returns an IntSize, and using it in platform
accessibility code.

No new tests. No change in behavior.

* accessibility/AccessibilityMenuListOption.h:
(WebCore::AccessibilityMenuListOption::canHaveChildren):
* accessibility/AccessibilityMenuListPopup.h:
(WebCore::AccessibilityMenuListPopup::elementRect):
* accessibility/AccessibilityObject.h:
(WebCore::AccessibilityObject::size):
(WebCore::AccessibilityObject::pixelSnappedSize):
* accessibility/AccessibilityRenderObject.cpp:
(WebCore):
* accessibility/AccessibilityRenderObject.h:
(AccessibilityRenderObject):
* accessibility/AccessibilitySlider.cpp:
(WebCore):
* accessibility/AccessibilitySlider.h:
(AccessibilitySliderThumb):
* accessibility/AccessibilityTableColumn.cpp:
(WebCore):
* accessibility/AccessibilityTableColumn.h:
(AccessibilityTableColumn):
* accessibility/AccessibilityTableHeaderContainer.cpp:
(WebCore):
* accessibility/AccessibilityTableHeaderContainer.h:
(AccessibilityTableHeaderContainer):
* accessibility/gtk/WebKitAccessibleInterfaceComponent.cpp:
(webkitAccessibleComponentGetExtents):
* accessibility/gtk/WebKitAccessibleInterfaceImage.cpp:
(webkitAccessibleImageGetImagePosition):
(webkitAccessibleImageGetImageSize):
* accessibility/mac/WebAccessibilityObjectWrapper.mm:
(-[WebAccessibilityObjectWrapper position]):
(-[WebAccessibilityObjectWrapper accessibilityAttributeValue:]):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114031 268f45cc-cd09-0410-ab3c-d52691b4dbfc