auto merge of #529 : eschweic/servo/master, r=pcwalton

Add a quadtree implementation to allow the compositor to keep track of which tiles have been rendered and which haven't.

r? @pcwalton
Merge pull request #530 from eschweic/master

Revert line height changes
Reapply "Add initial support for the line-height property. Line height is only based on the tallest box in each line and does not factor in the vertical-alignment. Improves whitespace handling by passing the whitespace state between function invocations."

This reverts commit 0bb3fbdde0b59a5d3df38a7fd7b970633300585c.
Fix line height for "normal" line-height styles.
Fix computing line height for generic boxes and images.
auto merge of #532 : jrfeenst/servo/line-height3, r=pcwalton

Wikipedia, lipsum, and everything else I looked at seems fine now.
auto merge of #531 : eschweic/servo/master, r=metajack

There is now a SharedChan from the compositor to the renderer. Using this, tiles are re-rendered the tiles at a higher resolution after zooming (this is currently bound to a MouseClickUp event). Also, extra texture layers are deleted, which fixes a bug where old content was being displayed when a new paint message was sent.

Depends on rust-layers: 1e1e359da32c9d0ddb4f93b505a658d669008426
Remove slow debug code from box.rs.
auto merge of #533 : pcwalton/servo/slow-debug-code, r=metajack

r? @metajack
Make quadtrees generic
Show the error massage if 'o' option is passed.
It's actually uname -m lying.
auto merge of #537 : GlitchMr/servo/darwin-uname-m, r=metajack

I know that this is very small commit, but I guess it still counts, as comment simply lies.
Address pcwalton's comments
auto merge of #535 : saneyuki/servo/o-opt, r=metajack

I think that we should show the error message until we restore the feature outputting the rendering result to a file.
Add helper functions for floats
Added floats to the flow tree
Allow floats to have specified heights
Fix up problems with float placement
Stop crashing when building the flow tree