initial implement for inline background
Add extra debugging information.
When `window.close()` is called, we should just ask the compositor to exit
normally.

The old code made the mistake of attempting to shutdown the associated
pipelines itself, which caused race conditions with the constellation and
compositor, as they expect to be able to drain their message queues
before exiting.
Changes the Constellation shutdown procedure to a message and response
from the Compositor instead of a message with an immediate callback.

The problem was that the old model introduced a potential deadlock. If
the Constellation had a pending RenderReadyMsg in its queue when the
ExitMsg arrived from the Compositor, the Compositor would exit its
message loop and wait for the response from the Constellation. But,
the Constellation would send a SetIds message to the Compositor, which
also required a response - resulting in deadlock.
Also handle the exit after load and output file cases for ref tests
Handle GLFW initialization failure

I hit this when trying to run servo in an ssh session. It hit an rtabort with
"fatal runtime error: thread-local pointer is null. bogus!" The exit is
required because at this point, the runtime is in a very weird state, and a
fail is going to explode even more violelently than the original unwrap did.
auto merge of #1502 : cmr/servo/handle_init_error, r=pcwalton

I hit this when trying to run servo in an ssh session. It hit an rtabort with
"fatal runtime error: thread-local pointer is null. bogus!" The exit is
required because at this point, the runtime is in a very weird state, and a
fail is going to explode even more violelently than the original unwrap did.
some refactor & add comment
auto merge of #1494 : ksh8281/servo/inline_add, r=pcwalton

initial implement for inline background
it makes same result in "src/test/html/inline_bg_color_simple.html" with firefox
auto merge of #1500 : larsbergstrom/servo/content_fixup, r=metajack

r? @metajack
Implement Node::replaceChild()

Implements Node:replaceChild() according to spec below:
http://dom.spec.whatwg.org/#concept-node-replace

Closes #1430.