https://bugs.webkit.org/show_bug.cgi?id=92043

Reviewed by James Robinson.

If accelerated compositing is enabled, WebWidget::paint reads back from
the compositor rather than re-painting the widget. That approach works
well if the canvas we're rendering into is at a similar resolution to
the pixels in the compositor, but if the canvas has been scaled (e.g.,
to help the user disambiguate links), then reading back from the
compositor will cause aliasing artifacts.

This patch adds an option to paint to let the embedder request a
software re-rendering of the widget to avoid these aliasing artifacts.

* public/WebWidget.h:
(WebKit::WebWidget::paint):
* src/WebPagePopupImpl.cpp:
(WebKit::WebPagePopupImpl::paint):
* src/WebPagePopupImpl.h:
(WebPagePopupImpl):
* src/WebPopupMenuImpl.cpp:
(WebKit::WebPopupMenuImpl::paint):
* src/WebPopupMenuImpl.h:
* src/WebViewImpl.cpp:
(WebKit::canvasBackgroundForTransparencey):
(WebKit):
(WebKit::WebViewImpl::paint):
* src/WebViewImpl.h:
(WebViewImpl):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@126095 268f45cc-cd09-0410-ab3c-d52691b4dbfc