Impelemented zooming and slightly better scrolling.
Merge with pcwalton's updated branch
Changed texturing mode to LINEAR for better zooming
Merge onto mozilla/servo master
Merge branch 'master' of https://github.com/mozilla/servo
Merge branch 'master' of https://github.com/mozilla/servo
Add quadtree implementation
Merge branch 'master' of https://github.com/mozilla/servo
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
Revert "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 7dcff2b5ff83faf44c24c1e5872b0a5dd850b1ae, reversing
changes made to 93eea6b2e87adedf833790d045bf69417ca9b7e3.
Merge pull request #530 from eschweic/master

Revert line height changes
Implement dynamic resolution, messaging from compositor to renderer, delete unused texture layers
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
Show the error massage if 'o' option is passed.