De-inline KURL equality operators.

Keeping them inline results in compilation issues with blink bindings
of media interfaces that use URLs.

This is a requirement for crrev.com/c/1389998

Bug: 704136
Change-Id: I4d87e2f6c19f9a91a3b51eee40f2cb7d59b5d56f
Reviewed-on: https://chromium-review.googlesource.com/c/1401044
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621547}