Update servo-media. Fixes discarded frames during player setup

Update web-platform-tests to revision 6087baf4a83e7953112242be9fd6e719797ebdf6

Bug 1509027 - Use more restricted scope for Treeherder routes

https://bugzilla.mozilla.org/show_bug.cgi?id=1509027

Cleanup constellation after nll

Use the base Ubuntu distro instead of LinuxMint in './mach bootstrap'

Fixup the issue related with an incorrect distro version string handling

Kill test processes whenever any error occurs

Update web-platform-tests to revision 5349c6a6327372f856ecbe07d863d468a4236726

Minor pull request template cleanup

Introduce NavigationPreloadManager for ServiceWorkerRegistration

Update web-platform-tests to revision 2d5385793ade85b7268ee86db4535a1baeb508ab

Cancel animations that affect nodes that do not participate in layout.

Add a test for dealing with multiple image loading tasks when the list of available images is usable.

Add info about building on Linux Mint to README

Remove redundant `.clone()`s

Update web-platform-tests to revision 912d5081b62d6e6a2f847935c82722e31cca7a1f

Add debug output for webdriver commands.

Delay setting the constellation's active browser id until the context exists.

Add headless support to servodriver harness.

Add automated test for servodriver harness.

Make SSL tests work in servodriver.

performance.rs

Added the specification link

Changed the queue_entry function

Implemented the following :
 a) Added the maxSize Field to the PerformanceEntryList structure.
 b) Implemented the clearResourceTimings, setResourceTimingBufferSize, onresourcetimingbufferfull fuctions for the Performance Structure according to the Interface Specification given at : https://w3c.github.io/resource-timing/#sec-extensions-performance-interface