* Part 1. Move IsLocalRefURL to nsContentUtils to reuse this function. (port-rewrite)
`IsLocalRefURL` is originally designed to be used by URLValue only.
Since we need this function in SVGUseElement::LookupHref too, move it to nsContentUtils as a util function.
* Revert "Part 1. Move IsLocalRefURL to nsContentUtils to reuse this function. (port-rewrite)"
This reverts commit 19f010c62022e269f99066a8d90e3522fe31adaf.
* Part 1. Duplicate IsLocalRefURL to nsContentUtils to reuse this function.
`IsLocalRefURL` is originally designed to be used by URLValue only.
Since we need this function in SVGUseElement::LookupHref too, duplicate it to nsContentUtils as a util function.
This is a duplication because CSSValue uses stringbuffers and not nsStrings.
While Bug 1356060 - "Just use nsString in URLValueData" converts this use from stringbuffer to nsString, it builds on a bunch of vartype refactoring (nsString vs. nsAString, etc.) which is too much of a headache to deal with just to deduplicate this simple function.
* Part 2. Implement nsSVGEffects::GetBaseURLForLocalRef to export local-ref-url-resolving logic.
ResolveURLUsingLocalRef is designed to be internally used by nsSVGEffects::Get-{SVGEffect}-URI functions.
Since we also need it in SVGUseElement::LookupHref, make it public in nsSVGEffects.
* Part 3. Resolve local-ref in SVGUseElement::LookupHref by nsSVGEffects::GetBaseURLForLocalRef.
* Part 4. Reftest for using local-ref as xlink:href value.
