Use common.dart to re-export commonly used entities.

pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart

Index: pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
index 8ca7b0e4274a640052c4c0523268d4c958e73ca7..4fc5ab6dd7ac8d1f0325182c82a61d3fa1575b79 100644
--- a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
@@ -78,9 +78,8 @@ class RuntimeTypeGenerator {
                                        FunctionType type) {
       assert(method.isImplementation);
       jsAst.Expression thisAccess = new jsAst.This();
-      Node node = method.node;
       ClosureClassMap closureData =
-          compiler.closureToClassMapper.closureMappingCache[node];
+          compiler.closureToClassMapper.closureMappingCache[method.node];
       if (closureData != null) {
         ClosureFieldElement thisLocal =
             closureData.freeVariableMap[closureData.thisLocal];