[chromium] Flip transition painting delayed with threaded animations

[chromium] Flip transition painting delayed with threaded animations
https://bugs.webkit.org/show_bug.cgi?id=82571

Patch by Dana Jansens <danakj@chromium.org> on 2012-04-09
Reviewed by Adrienne Walker.

Source/WebCore:

This allows for prepainting to see and paint layers that are not facing
the camera but have animating transforms. This is needed to prepaint
animations that "flip" layers around to make the front visible.

The changes are to add a backFaceIsVisible() helper function in
CCLTHCommon. This is used like before to cull non-double sided
layers, but culling is prevented on main thread when the screen
space transform is unknown due to animation. We add new
helper methods transformToScreenIsKnown() to identify this.

However the layer is not actually visible, so we set the
visibleLayerRect to be empty in this case.

The calculateVisibleLayerRect needs to use the backFaceIsVisible()
helper, so we move it into the .cpp file where it belongs, and make
it static to the file since it is not used outide of CCLTHCommon.cpp
at all.

Unit test: CCLayerTreeHostCommonTest.verifyBackFaceCulling

* platform/graphics/chromium/cc/CCLayerTreeHostCommon.cpp:
(WebCore):
(WebCore::backFaceIsVisible):
(WebCore::calculateVisibleLayerRect):
(WebCore::layerOpacityIsOpaque):
(WebCore::transformToParentIsKnown):
(WebCore::transformToScreenIsKnown):
(WebCore::layerShouldBeSkipped):
(WebCore::calculateDrawTransformsAndVisibilityInternal):
(WebCore::walkLayersAndCalculateVisibleLayerRects):
* platform/graphics/chromium/cc/CCLayerTreeHostCommon.h:
(WebCore):

Source/WebKit/chromium:

* tests/CCLayerTreeHostCommonTest.cpp:
(WebKitTests::TEST):
(WebKitTests):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@113602 268f45cc-cd09-0410-ab3c-d52691b4dbfc