Update url for ARIA IDL spec.

The implementation was based on a PR that has now been merged.

TBR=aboxhall@chromium.org,haraken@chromium.org

Bug: 844540
Change-Id: I9daec3930c465428c38c52cfc1c107b30005721e
Reviewed-on: https://chromium-review.googlesource.com/1080216Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563127}

third_party/blink/renderer/core/dom/accessibility_role.idl

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // ARIA reflection
-// https://github.com/w3c/aria/pull/708/files
+// https://w3c.github.io/aria/#idl-interface
 [
     NoInterfaceObject,
     RuntimeEnabled=AccessibilityObjectModel

third_party/blink/renderer/core/dom/aria_attributes.idl

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // ARIA reflection
-// https://github.com/w3c/aria/pull/708/files
+// https://w3c.github.io/aria/#idl-interface
 [
     NoInterfaceObject,
     RuntimeEnabled=AccessibilityObjectModel