https://bugs.webkit.org/show_bug.cgi?id=13897
<rdar://problem/5232483>

Reviewed by Dan Bernstein.

When hovering over a file input element, we set the button's state to active
to differentiate dragging one file over the input element (which populates that
element) versus over the document (which would load the file into the view).

* html/HTMLInputElement.cpp:
(WebCore::HTMLInputElement::HTMLInputElement):
(WebCore::HTMLInputElement::canReceiveDroppedFiles):
(WebCore::HTMLInputElement::setCanReceiveDroppedFiles): If set, the element
is updated, which sets the active state on the button control.
* html/HTMLInputElement.h: Add a boolean member representing whether the file
input can receive dropped files.
* page/DragController.cpp:
(WebCore::DragController::DragController): Update/set the file input that
can receive dropped files.
(WebCore::DragController::dragExited):
(WebCore::DragController::tryDocumentDrag):
(WebCore::DragController::concludeEditDrag):
* page/DragController.h:
* rendering/RenderFileUploadControl.cpp:
(WebCore::RenderFileUploadControl::updateFromElement): Sets the button active
state if the input can receive dropped files.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@99369 268f45cc-cd09-0410-ab3c-d52691b4dbfc