Bug 1481927. Always pass an object from the "relevant global" to Web IDL APIs that have a non-wrapper-cached "this". r=bholley

Differential Revision: https://phabricator.services.mozilla.com/D4491

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

dom/bindings/Codegen.py

@@ -7580,9 +7580,15 @@ class CGPerSignatureCall(CGThing):
         elif needScopeObject(returnType, arguments, self.extendedAttributes,
                              descriptor.wrapperCache, True,
                              idlNode.getExtendedAttribute("StoreInSlot")):
-            needsUnwrap = True
-            needsUnwrappedVar = True
-            argsPre.append("unwrappedObj ? *unwrappedObj : obj")
+            # The scope object should always be from the relevant
+            # global.  Make sure to unwrap it as needed.
+            cgThings.append(CGGeneric(dedent(
+                """
+                JS::Rooted<JSObject*> unwrappedObj(cx, js::CheckedUnwrap(obj));
+                // Caller should have ensured that "obj" can be unwrapped already.
+                MOZ_DIAGNOSTIC_ASSERT(unwrappedObj);
+                """)))
+            argsPre.append("unwrappedObj")
 
         if needsUnwrap and needsUnwrappedVar:
             # We cannot assign into obj because it's a Handle, not a

dom/encoding/TextEncoder.cpp

@@ -31,7 +31,7 @@ TextEncoder::Encode(JSContext* aCx,
     return;
   }
 
-  JSAutoRealmAllowCCW ar(aCx, aObj);
+  JSAutoRealm ar(aCx, aObj);
   JSObject* outView = Uint8Array::Create(
     aCx, utf8.Length(), reinterpret_cast<const uint8_t*>(utf8.BeginReading()));
   if (!outView) {