Further reduce use of Element in codegen.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 9670004de3495b9d97bbcbbc26218d6c84964481..a48bef41e19dac00e3194113c9a85d4f0fbfc94b 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -1474,6 +1474,18 @@ class _CompilerCommonElements implements CommonElements {
   ConstructorElement _filledListConstructor;
   ConstructorElement get filledListConstructor =>
       _filledListConstructor ??= listClass.lookupConstructor("filled");
+
+  // TODO(johnniwinther): Change types to `ClassElement` when these are not
+  // called with unrelated elements.
+  bool isNumberOrStringSupertype(/*Class*/ Element element) {
+    return element == coreLibrary.find('Comparable');
+  }
+
+  bool isStringOnlySupertype(/*Class*/ Element element) {
+    return element == coreLibrary.find('Pattern');
+  }
+
+  bool isListSupertype(/*Class*/ Element element) => element == iterableClass;
 }
 
 class CompilerDiagnosticReporter extends DiagnosticReporter {