Bug 1572349 - Add Document::ResolveWithBaseURI r=bzbarsky

This adds a helper method that enables simpler code in D41047 and D36714.

Differential Revision: https://phabricator.services.mozilla.com/D41902

--HG--
extra : moz-landing-system : lando

dom/base/Document.cpp

@@ -331,6 +331,7 @@
 #include "mozilla/PendingFullscreenEvent.h"
 #include "mozilla/RestyleManager.h"
 #include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ResultExtensions.h"
 #include "nsHTMLTags.h"
 #include "MobileViewportManager.h"
 #include "NodeUbiReporting.h"
@@ -5750,6 +5751,14 @@ void Document::SetBaseURI(nsIURI* aURI) {
   RefreshLinkHrefs();
 }
 
+Result<nsCOMPtr<nsIURI>, nsresult> Document::ResolveWithBaseURI(
+    const nsAString& aURI) {
+  nsCOMPtr<nsIURI> resolvedUri;
+  MOZ_TRY(
+      NS_NewURI(getter_AddRefs(resolvedUri), aURI, nullptr, GetDocBaseURI()));
+  return std::move(resolvedURI);
+}
+
 URLExtraData* Document::DefaultStyleAttrURLData() {
   MOZ_ASSERT(NS_IsMainThread());
   nsIURI* baseURI = GetDocBaseURI();

dom/base/Document.h

@@ -910,6 +910,11 @@ class Document : public nsINode,
 
   void SetBaseURI(nsIURI* aURI);
 
+  /**
+   * Resolves a URI based on the document's base URI.
+   */
+  Result<nsCOMPtr<nsIURI>, nsresult> ResolveWithBaseURI(const nsAString& aURI);
+
   /**
    * Return the URL data which style system needs for resolving url value.
    * This method attempts to use the cached object in mCachedURLData, but