Rewrite manifest.py to make including local changes safer (not very backwards compatible)
Allow running tests from an external server root.

This is needed for supporting use cases where testsuites outside
wpt are run using the server in a wpt checkout. It also changes the
manifest format in a way that causes the file path to be derived from
the url unless otherwise specified.
fixup review issues
One test is manual and make sure the constructor test fails properply if PointerEvent isn't supported
Remove unrelated change.
Update resource timing test to reduce flakiness.
fixup! Update resource timing test to reduce flakiness.
Merge pull request #1291 from w3c/jgraham/resource_timing

Update resource timing test to reduce flakiness.
Create eventsource-request-cancellation.htm

Update the file per #285 issuecomment-47893559
Improve assert message
Add sleep method to message.py

 -This resolves #285 and closes #241
Remove trailing whitespace
Merge pull request #1292 from Honry/pr285

new test for EventSource + request cancellation
Merge pull request #1281 from w3c/jgraham/serve_alternate_root

Allow running tests from a path outside the test root.
three-way merge with rust-url

https://github.com/servo/rust-url/blob/master/src/urltestdata.txt
remove duplicated test
Fixing All_Pointer_Events issue

This also fixes work of this test in FF
Merge pull request #1293 from rubys/merge_with_rust

three-way merge with rust-url
Fix XHR server side to actually write a response for chunked output.
Update test runner for changes in the manifest API.