Bug 1357432 (#750)

* 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.

1 files changed, 7 insertions, 0 deletions

diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index 9ae6d2155..c255f813a 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -2730,6 +2730,13 @@ public:
 
   static bool AttemptLargeAllocationLoad(nsIHttpChannel* aChannel);
 
+  /**
+   * Detect whether a string is a (CSS) local-url.
+   * https://drafts.csswg.org/css-values/#local-urls
+   */
+  static bool
+  IsLocalRefURL(const nsString& aString);
+
 private:
   static bool InitializeEventTable();