Make speedscope work when hosted on an arbitrary URL or served from file://

[jlfwong]

This makes it easier to download speedscope to run totally offline, and makes embedding it into other applications easier since it no longer depends on specific URL paths.

[coveralls]

Pull Request Test Coverage Report for Build 184

• 0 of 5 (0.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 37.647%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
application.tsx	0	5	0.0%

Files with Coverage Reduction	New Missed Lines	%
lru-cache.ts	1	86.24%

Totals
Change from base Build 182:	-0.1%
Covered Lines:	1110
Relevant Lines:	2851

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💛 - Coveralls