Remove unused API.

dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart

Index: dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart b/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
index 2e98925a21c83a16ceb5894176c248d04712195d..9289249a552eac3fe83179e349b4d63c6379ae3c 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
@@ -287,8 +287,6 @@ abstract class ElementX implements Element {
 
   FunctionElement asFunctionElement() => null;
 
-  static bool isInvalid(Element e) => e == null || e.isErroneous();
-
   bool get isAbstract => modifiers.isAbstract();
   bool isForeign(Compiler compiler) => getLibrary() == compiler.foreignLibrary;
 
@@ -1872,22 +1870,6 @@ abstract class BaseClassElementX extends ElementX implements ClassElement {
     return null;
   }
 
-  Element lookupSuperInterfaceMember(String memberName,
-                                     LibraryElement fromLibrary) {
-    bool isPrivate = isPrivateName(memberName);
-    for (InterfaceType t in interfaces) {
-      ClassElement cls = t.element;
-      Element e = cls.lookupLocalMember(memberName);
-      if (e == null) continue;
-      // Private members from a different library are not visible.
-      if (isPrivate && !identical(fromLibrary, e.getLibrary())) continue;
-      // Static members are not inherited.
-      if (e.modifiers.isStatic()) continue;
-      return e;
-    }
-    return null;
-  }
-
   /**
    * Find the first member in the class chain with the given [selector].
    *
@@ -2008,13 +1990,6 @@ abstract class BaseClassElementX extends ElementX implements ClassElement {
     return validateConstructorLookupResults(selector, result, noMatch);
   }
 
-  Element lookupFactoryConstructor(Selector selector,
-                                   [Element noMatch(Element)]) {
-    String constructorName = selector.name;
-    Element result = localLookup(constructorName);
-    return validateConstructorLookupResults(selector, result, noMatch);
-  }
-
   Link<Element> get constructors {
     // TODO(ajohnsen): See if we can avoid this method at some point.
     Link<Element> result = const Link<Element>();