Use interceptors to handle runtime types.

dart/sdk/lib/_internal/lib/interceptors.dart

Index: dart/sdk/lib/_internal/lib/interceptors.dart
diff --git a/dart/sdk/lib/_internal/lib/interceptors.dart b/dart/sdk/lib/_internal/lib/interceptors.dart
index 9dff6fbd4f70356211521212c6a648243889d62c..7851c3c806fb8261551703bcc82284c046ef19b4 100644
--- a/dart/sdk/lib/_internal/lib/interceptors.dart
+++ b/dart/sdk/lib/_internal/lib/interceptors.dart
@@ -7,29 +7,32 @@ library _interceptors;
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import "dart:_collection-dev" as _symbol_dev show Symbol;
-import 'dart:_js_helper' show allMatchesInStringUnchecked,
-                              Null,
-                              JSSyntaxRegExp,
-                              Primitives,
-                              checkNull,
-                              checkNum,
-                              checkString,
-                              defineProperty,
-                              getRuntimeType,
-                              regExpGetNative,
-                              stringContainsUnchecked,
-                              stringLastIndexOfUnchecked,
-                              stringReplaceAllFuncUnchecked,
-                              stringReplaceAllUnchecked,
-                              stringReplaceFirstUnchecked,
-                              lookupDispatchRecord,
-                              StringMatch,
-                              firstMatchAfter;
+import 'dart:_js_helper' show
+    JSSyntaxRegExp,
+    Null,
+    Primitives,
+    StringMatch,
+    allMatchesInStringUnchecked,
+    checkNull,
+    checkNum,
+    checkString,
+    defineProperty,
+    firstMatchAfter,
+    getRuntimeType,
+    lookupDispatchRecord,
+    regExpGetNative,
+    runtimeTypeToString,
+    stringContainsUnchecked,
+    stringLastIndexOfUnchecked,
+    stringReplaceAllFuncUnchecked,
+    stringReplaceAllUnchecked,
+    stringReplaceFirstUnchecked;
 import 'dart:_foreign_helper' show JS, JS_EFFECT;
-
+import 'dart:_js_names' show extractKeys, unmangleGlobalNameIfPreservedAnyways;
 part 'js_array.dart';
 part 'js_number.dart';
 part 'js_string.dart';
+part 'js_types.dart';
 
 String _symbolToString(Symbol symbol) => _symbol_dev.Symbol.getName(symbol);
 
@@ -312,7 +315,6 @@ abstract class JSMutableIndexable extends JSIndexable {
 abstract class JSObject {
 }
 
-
 /**
  * Interceptor base class for JavaScript objects not recognized as some more
  * specific native type.
@@ -326,7 +328,6 @@ abstract class JavaScriptObject extends Interceptor implements JSObject {
   Type get runtimeType => JSObject;
 }
 
-
 /**
  * Interceptor for plain JavaScript objects created as JavaScript object
  * literals or `new Object()`.
@@ -335,7 +336,6 @@ class PlainJavaScriptObject extends JavaScriptObject {
   const PlainJavaScriptObject();
 }
 
-
 /**
  * Interceptor for unclassified JavaScript objects, typically objects with a
  * non-trivial prototype chain.