Remove needless rust-png dependency.
Use virtualenv2 in tests/wpt/run.sh if installed
Add lint for type-checking transmutes
Fix layout of Create Account / Login when rendering Wikipedia.

When calculating the preferred width for a block, accumulate
the left and right float widths of children separately, which
is then max'ed with the normal flow widths later on.

Ref bug #2554 - improves the layout of the top bar.
Block layout RPC on the first layout call
Merge pull request #3272 from glennw/wikipedia-layout

Fix layout of Create Account / Login when rendering Wikipedia.
Merge pull request #3258 from Manishearth/transmute_lint

Add lint for type-checking transmutes; r=jack
Merge pull request #3268 from saneyuki/dep

Remove needless rust-png dependency.
Merge pull request #3271 from duncankl/virtualenv2-fix

Use virtualenv2 in tests/wpt/run.sh if installed
Move Attr helper methods to AttrHelpers trait to avoid to touch them from layout task.
Move Attr::local_name() to AttrHelpers/AttrHelpersForLayout.
Merge pull request #3274 from saneyuki/attr

Move Attr::set_value and Attr::value out of the Attr impl
Fix loading of file URLs with spaces
Merge pull request #3280 from metajack/path-with-spaces

Fix loading of file URLs with spaces
Return error when unable to create a file path from url.
net: Premultiply alpha in PNGs.

Closes #2857.
Run build-cef last so that tests don't cause a rebuild.
Merge pull request #3281 from pcwalton/premultiply-alpha

net: Premultiply alpha in PNGs.
Partial fix for background images on wikipedia pages.

This fixes the visual artifacts seen at the top of wikipedia pages by:
 - Setting clipping rect to avoid images going outside their bounds.
 - Handling case of background-position being >= 100% such that wrapping is required.

However, the gradient is not currently visible on wikipedia. This relies on bug #1997 being fixed.
Merge pull request #3284 from glennw/file-loader-fix

Return error when unable to create a file path from url.