Bug 1309970. Add a way to return frozen arrays to chrome callers with a .contains defined on them, returning the same value as .includes. r=qdot

dom/bindings/Codegen.py

@@ -7205,6 +7205,10 @@ def wrapArgIntoCurrentCompartment(arg, value, isMember=True):
     return wrap
 
 
+def needsContainsHack(m):
+    return m.getExtendedAttribute("ReturnValueNeedsContainsHack")
+
+
 class CGPerSignatureCall(CGThing):
     """
     This class handles the guts of generating code for a particular
@@ -7578,6 +7582,22 @@ class CGPerSignatureCall(CGThing):
             # the compartment we do our conversion in but after we've finished
             # the initial conversion into args.rval().
             postConversionSteps = ""
+            if needsContainsHack(self.idlNode):
+                # Define a .contains on the object that has the same value as
+                # .includes; needed for backwards compat in extensions as we
+                # migrate some DOMStringLists to FrozenArray.
+                postConversionSteps += dedent(
+                    """
+                    if (args.rval().isObject() && nsContentUtils::ThreadsafeIsCallerChrome()) {
+                      JS::Rooted<JSObject*> rvalObj(cx, &args.rval().toObject());
+                      JS::Rooted<JS::Value> includesVal(cx);
+                      if (!JS_GetProperty(cx, rvalObj, "includes", &includesVal) ||
+                          !JS_DefineProperty(cx, rvalObj, "contains", includesVal, JSPROP_ENUMERATE)) {
+                        return false;
+                      }
+                    }
+
+                    """)
             if self.idlNode.getExtendedAttribute("Frozen"):
                 assert self.idlNode.type.isSequence() or self.idlNode.type.isDictionary()
                 freezeValue = CGGeneric(
@@ -13568,7 +13588,8 @@ class CGBindingRoot(CGThing):
         def descriptorHasChromeOnly(desc):
             ctor = desc.interface.ctor()
 
-            return (any(isChromeOnly(a) for a in desc.interface.members) or
+            return (any(isChromeOnly(a) or needsContainsHack(a)
+                        for a in desc.interface.members) or
                     desc.interface.getExtendedAttribute("ChromeOnly") is not None or
                     # JS-implemented interfaces with an interface object get a
                     # chromeonly _create method.  And interfaces with an

dom/bindings/parser/WebIDL.py

@@ -4213,6 +4213,7 @@ class IDLAttribute(IDLInterfaceMember):
               identifier == "NewObject" or
               identifier == "UnsafeInPrerendering" or
               identifier == "NeedsSubjectPrincipal" or
+              identifier == "ReturnValueNeedsContainsHack" or
               identifier == "BinaryName"):
             # Known attributes that we don't need to do anything with here
             pass

dom/bindings/test/test_dom_xrays.html

@@ -184,6 +184,17 @@ function test()
   isnot(languages1, languages2.wrappedJSObject,
         "Must have distinct arrays no matter how we slice it");
 
+  // Check that DataTransfer's .types has the hack to alias contains()
+  // to includes().
+  var dataTransfer = new win.DataTransfer("foo", true);
+  is(dataTransfer.types.contains, dataTransfer.types.includes,
+     "Should have contains() set up as an alias to includes()");
+  // Waive Xrays on the dataTransfer itself, since the .types we get is
+  // different over Xrays vs not.
+  is(dataTransfer.wrappedJSObject.types.contains, undefined,
+     "Underlying object should not have contains() set up as an alias to " +
+     "includes()");
+
   SimpleTest.finish();
 }
 

dom/webidl/DataTransfer.webidl

@@ -17,7 +17,9 @@ interface DataTransfer {
   [Throws]
   void setDragImage(Element image, long x, long y);
 
-  [Pure, Cached, Frozen, NeedsSubjectPrincipal]
+  // ReturnValueNeedsContainsHack on .types because lots of extension
+  // code was expecting .contains() back when it was a DOMStringList.
+  [Pure, Cached, Frozen, NeedsSubjectPrincipal, ReturnValueNeedsContainsHack]
   readonly attribute sequence<DOMString> types;
   [Throws, NeedsSubjectPrincipal]
   DOMString getData(DOMString format);