Commits on Sep 29, 2015

1. 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 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.

   

   pcwalton committed Sep 29, 2015

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