Bug 1553018 part 6. Allow [Pref] annotations on dictionary members. r=edgar

Differential Revision: https://phabricator.services.mozilla.com/D32947

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

dom/bindings/parser/WebIDL.py

@@ -4580,7 +4580,8 @@ class IDLArgument(IDLObjectWithIdentifier):
             elif identifier == "TreatNonCallableAsNull":
                 self._allowTreatNonCallableAsNull = True
             elif (self.dictionaryMember and
-                  (identifier == "ChromeOnly" or identifier == "Func")):
+                  (identifier == "ChromeOnly" or identifier == "Func" or
+                   identifier == "Pref")):
                 if not self.optional:
                     raise WebIDLError("[%s] must not be used on a required "
                                       "dictionary member" % identifier,

dom/bindings/test/TestCodeGen.webidl

@@ -1220,6 +1220,12 @@ dictionary DictWithConditionalMembers {
   long funcControlledMember;
   [ChromeOnly, Func="nsGenericHTMLElement::LegacyTouchAPIEnabled"]
   long chromeOnlyFuncControlledMember;
+  // We need a pref name that's in StaticPrefList.h here.
+  [Pref="browser.dom.window.dump.enabled"]
+  long prefControlledMember;
+  [Pref="browser.dom.window.dump.enabled", ChromeOnly,
+   Func="TestFuncControlledMember"]
+  long chromeOnlyFuncAndPrefControlledMember;
 };
 
 interface TestIndexedGetterInterface {