CacheKey constructor should take Request by reference

[jdm]

In CacheKey's new method in http_cache.rs it takes a Request argument by value, but then it calls a method on it that only needs a borrowed value. We clone request objects every time we call CacheKey::new, and this is wasteful.

Code: components/net/http_cache.rs

No need to run tests; if it builds, that's good enough for a pull request.

[highfive]

Hi! If you have any questions regarding this issue, feel free to make a comment here, or ask it in the #servo channel in IRC.

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[Tugdual]

@highfive: assign me

[highfive]

Hey @Tugdual! Thanks for your interest in working on this issue. It's now assigned to you!

[PeaceRebel]

@jdm , I'm new to rust. Instead of cloning, passing a reference would get it done, right?

[jdm]

@PeaceRebel Yes, that is what I suggested. It looks like @Tugdual is working on this, however.