Implement <meta name=viewport> handling
Translate <meta name=viewport> as according to [CSS Device Adaption § 9](http://dev.w3.org/csswg/css-device-adapt/#viewport-meta)
Note: as the PR currently stands, handling `<meta name=viewport>` elements always occurs. This is probably not desired for some contexts (e.g. desktop), but I'm unsure of how to conditionally handle elements based on that.
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Refactor FormControl trait
The trait is now implemented for HTMLFooElement instead of
&HTMLFooElement and does no longer require an impl body.
Suggested by @Manishearth
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Simplify stacking context creation
Have Fragment::create_stacking_context understand which stacking
contexts need layers and which do not. This simplifies the way it is
called and eliminates a bunch of code.
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Prior to this commit, `str_join` would skip empty items at the start of
the `Iterator` until it found a non-empty item. This contradicts
`SliceConcatExt::join` which doesn't skip anything.
Brought up in:
https://github.com/servo/servo/pull/7776#issuecomment-144317281
Have Fragment::create_stacking_context understand which stacking
contexts need layers and which do not. This simplifies the way it is
called and eliminates a bunch of code.
Make DisplayList hit testing a method on DisplayList
This will allow us to hit test into DisplayLists that are not directly
contained in StackingContexts, but instead are children of PaintLayers.
It also makes things slightly simpler.
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layout: Make the compositor rather than layout determine the position of 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 only the size of an iframe is
determined during layout, and the position is determined by the
compositor. Layout layerizes iframes and marks the iframe layers with
the appropriate subpage ID so that the compositor can place them
correctly.
Closes#7377.
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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 will allow us to hit test into DisplayLists that are not directly
contained in StackingContexts, but instead are children of PaintLayers.
It also makes things slightly simpler.
