each iframe.
The old code that attempted to do this during layout wasn't able to work
for multiple reasons: it couldn't know where the iframe was going to be
on the page (because of nested iframes), and at the time it was building
the display list for a fragment it couldn't know where that fragment was
going to be in page coordinates.
This patch rewrites that code so that both the sizes and positions of
iframes are determined by the compositor. Layout layerizes all iframes
and marks the iframe layers with the appropriate pipeline and subpage
IDs so that the compositor can place them correctly. This approach is
similar in spirit to Gecko's `RefLayer` infrastructure. The logic that
determines when it is time to take the screenshot for reftests has been
significantly revamped to deal with this change in delegation of
responsibility.
Additionally, this code removes the infrastructure that sends layout
data back to the layout task to be destroyed, since it is now all
thread-safe and can be destroyed on the script task.
The failing tests now fail because of a pre-existing bug related to
intrinsic heights and borders on inline replaced elements. They happened
to pass before because we never rendered the iframes at all, which meant
they never had a chance to draw the red border the tests expect to not
render!
Closes#7377.
This should fix a bug where hidden iframes are not properly clipped
away from the compositor scene. This commit adds a test for this
behavior.
Fixes#6849.
When an iframe is created with display:none it sets the root layer to be
zero width and height. When updating the rect of the iframe from layout
send the entire rect rather than just the new origin, which handles the case
where the iframe has been made visible and now has a non-zero rect.
Instead of taking margin size into account twice when positioning
layers, just rely on the absolute position calculated during display
list construction.
Add iframe tests to their own subdirectory and add another test case
that used to trigger a fatal error. The new test case uses the
"allow-scripts" sandbox attribute to work around a script task failure
caused by the child frame sharing the same script task as the parent.
