jumping to a named anchor

https://bugs.webkit.org/show_bug.cgi?id=28899

Reviewed by Adam Roben.

* accessibility/AXObjectCache.h:
(WebCore::AXObjectCache::):
Added declaration for handleScrolledToAnchor(). Added a new entry to
the enum of accessibility notifications.

* accessibility/AccessibilityObject.cpp:
(WebCore::AccessibilityObject::firstAccessibleObjectFromNode):
Code moved from AccessibilityRenderObject::internalLinkElement() and
refactored slightly; walks the tree until it finds a Node (with a
renderer) whose accessibility is not ignored.

* accessibility/AccessibilityObject.h:
Added a declaration for firstAccessibleObjectFromNode().

* accessibility/AccessibilityRenderObject.cpp:
(WebCore::AccessibilityRenderObject::internalLinkElement):
Code moved to AccessibilityObject::firstAccessibleObjectFromNode().

* accessibility/chromium/AXObjectCacheChromium.cpp:
(WebCore::AXObjectCache::handleScrolledToAnchor):
Stubbed.

* accessibility/gtk/AXObjectCacheAtk.cpp:
(WebCore::AXObjectCache::handleScrolledToAnchor):
Stubbed.

* accessibility/mac/AXObjectCacheMac.mm:
(WebCore::AXObjectCache::postPlatformNotification):
Add a default case that returns early for notifications that Mac
doesn't handle.
(WebCore::AXObjectCache::handleScrolledToAnchor):
Stubbed.

* accessibility/win/AXObjectCacheWin.cpp:
(WebCore::AXObjectCache::handleScrolledToAnchor):
Post an AXScrolledToAnchor notification for the first accessible from
the anchor Node.
(WebCore::AXObjectCache::postPlatformNotification):
If the notification is AXFocusedUIElementChanged, fire an
EVENT_OBJECT_FOCUS. If the notification is AXScrolledToAnchor, fire
EVENT_SYSTEM_SCROLLINGSTART, matching Firefox.
(WebCore::AXObjectCache::handleFocusedUIElementChanged):
Code moved to postPlatformNotification().

* page/FrameView.cpp:
(WebCore::FrameView::scrollToAnchor):
Call AXObjectCache::handleScrolledToAnchor().

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@48367 268f45cc-cd09-0410-ab3c-d52691b4dbfc