Specifically, this patch adds support for these longhand properties:
-webkit-border-image-outset
-webkit-border-image-repeat
-webkit-border-image-slice
-webkit-border-image-source
-webkit-border-image-width
nsTextFrame didn't use the composition underline color if the
composition didn't have a foreground color defined. This patch makes it
use the underline color if foreground color is not defined.
Displayports only get acted upon when painting to the window, and the async scroll clips only get computed when we use a displayport.
In addition we change an assert because if we are painting to the window then our root reference frame is either a root frame, or a popup frame. In either case we should not be able to get to out of flows outside of the frame subtree rooted at the root reference frame by following placeholders.
Removing the "stop at ancestor" parameter from functions that compute AGR meant that nsLayoutUtils::GetAnimatedGeometryRootFor could no longer pass the display item's reference frame as the "stop at ancestor" which meant that the AGR could cross the reference frame for the item, which we don't want. So we make transformed frames into AGRs.
This makes the computation of display items whose frames are transformed tricky. We need the AGR of the transform item to be the ancestor AGR, not the underlying frame of the transform item (which is now an AGR). So we modify nsLayoutUtils::GetAnimatedGeometryRootFor to handle this. (The patch from bug 1205087 didn't suffer from this problem because it special cased the computation of the AGR of transform items. Leaving anybody who called nsLayoutUtils::GetAnimatedGeometryRootFor to get the wrong result.)
The computation of the AGR for scroll metadata in ContainerState::ProcessDisplayItems specifically bypassed nsLayoutUtils::GetAnimatedGeometryRootFor to avoid it's special processing of fixed background items. However we do want the AGR for scroll metadata to do this special processing of transform items. So we add a flag to bypass the fixed background behaviour and use it for the scroll metadata AGR.
This removes the "aStopAtAncestor" argument to agr computing functions. In most cases an AGR was passed for the stop at ancestor, so we'd stop at it anyway since it was an AGR. Most of the remaining cases the root reference frame was passed. And in a few cases something else was passed, which we probably don't want (returning something that isn't an AGR and isn't the root reference frame as an AGR).
The ShouldFixToViewport case is a little tricky. We want to get the AGR of the nearest viewport frame, but only if we don't have to cross our root reference frame to get it. This happens in practice for example when a select dropdown has background-attachment: fixed inside it.
Except for the ShouldFixToViewport bit, this patch is a subset of part 3 in bug 1205087 (which has more changes, and has been temporarily backed out, the remaining bits can hopefully land soon).
The ShouldFixToViewport part is by Timothy Nikkel <tnikkel@gmail.com>
