Remove 'FloatFlow'

Removes 'FloatFlow' in favor of FloatBlockFlow, which is cointained
inside BlockFlow in a 'has-a' relationship. This avoids a bunch of
duplicated code.

This patch is for:
https://github.com/mozilla/servo/issues/1281
Work around Rust bug causing nondeterministic CSS parse failure

The bug is mozilla/rust#10683 and there's no fix yet, plus it
would take us a while to upgrade Rust anyway.

Fixes #1258.
auto merge of #1328 : kmcallister/servo/properties, r=jdm

The bug is mozilla/rust#10683 and there's no fix yet, plus it would take us a while to upgrade Rust anyway.

Fixes #1258.
auto merge of #1321 : brunoabinader/servo/remove-floatflow, r=pcwalton

Removes 'FloatFlow' in favor of FloatBlockFlow, which is contained
inside BlockFlow in a 'has-a' relationship. This avoids a bunch of
duplicated code.

This patch is for:
https://github.com/mozilla/servo/issues/1281
http_loader: Don't tail-call for redirects

Serving suggestion: git show -w

Fixes #1325.

Some of the control-flow reorganization is for clarity rather than out of
necessity.
CSS: Add the 'visibility' property.

http://www.w3.org/TR/CSS21/visufx.html#visibility

'visibility: collapse' is not supported yet because tables are not, either.

This fixes #1329.
auto merge of #1330 : kmcallister/servo/http_loader, r=pcwalton

Serving suggestion: `git show -w`

Fixes #1325.

Some of the control-flow reorganization is for clarity rather than out of necessity.
auto merge of #1331 : SimonSapin/servo/visibility, r=pcwalton

http://www.w3.org/TR/CSS21/visufx.html#visibility

`visibility: collapse` is not supported yet because tables are not, either.

This fixes #1329.
Acid1 fix (fixed FloatFlow refactory)

While doing the FloatFlow refactory, I forgot to transpose a variable
assignment in assign_widths(). Also did a minor change in
bubble_widths() to avoid creating temporary variables in an iteration
loop.

This patch is for:
https://github.com/mozilla/servo/issues/1335
Merge pull request #1337 from brunoabinader/acid1_fix

Acid1 fix (fixed FloatFlow refactory)
Report exceptions to JS when the DOM implementation fails.

As a bonus, adds some debugging statements.
Add test.
Return None from get_graphics_metadata in headless compositor

This fixes servo -z.
Merge pull request #1304 from Ms2ger/exceptions

Report exceptions to JS when the DOM implementation fails.
Merge pull request #1339 from kmcallister/native_graphics_context

Return None from get_graphics_metadata in headless compositor
layout: Change `RenderBox` to an enum and shorten its name in
preparation for removing its `@`-ness.

Also removes a few text copies that were taking place.

This sure does remove a lot of code!