Add missing tracers for servo (#359) #400

Job	Run time
windows (--features debugmozjs)	21m 55s
windows (--features debugmozjs, aarch64-uwp-windows-msvc)	23m 2s
windows (--features debugmozjs, x86_64-uwp-windows-msvc)	19m 19s
windows	25m 34s
windows (aarch64-uwp-windows-msvc)	19m 46s
windows (x86_64-uwp-windows-msvc)	23m 47s
Integrity	17s
linux (--features debugmozjs)	15m 46s
linux	21m 55s
mac (--features debugmozjs)	22m 32s
mac	22m 16s
Result	1s
	3h 36m 10s

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