Support foreigns as external.

sdk/lib/_internal/compiler/js_lib/foreign_helper.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library _foreign_helper;
 
 import 'dart:_js_embedded_names' show JsGetName, JsBuiltin;
 
 /**
  * Emits a JavaScript code fragment parameterized by arguments.
@@ skipping 124 matching lines @@
  *
  * In the future we may extend [typeDescription] to include other aspects of the
  * behavior, for example, separating the returned types from the instantiated
  * types to allow the compiler to perform more optimizations around the code.
  *
  * This might be an extension of [JS] or a new function similar to [JS] with
  * additional arguments for the new information.
  */
 // Add additional optional arguments if needed. The method is treated internally
 // as a variable argument method.
-JS(String typeDescription, String codeTemplate,
-    [arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11])
-{}
+external JS(String typeDescription, String codeTemplate,
+    [arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11]);
 
 /**
  * Returns the isolate in which this code is running.
  */
-IsolateContext JS_CURRENT_ISOLATE_CONTEXT() {}
+external IsolateContext JS_CURRENT_ISOLATE_CONTEXT();
 
 abstract class IsolateContext {
   /// Holds a (native) JavaScript instance of Isolate, see
   /// finishIsolateConstructorFunction in emitter.dart.
   get isolateStatics;
 }
 
 /**
  * Invokes [function] in the context of [isolate].
  */
-JS_CALL_IN_ISOLATE(isolate, Function function) {}
+external JS_CALL_IN_ISOLATE(isolate, Function function);
 
 /**
  * Converts the Dart closure [function] into a JavaScript closure.
  *
  * Warning: This is no different from [RAW_DART_FUNCTION_REF] which means care
  * must be taken to store the current isolate.
  */
-DART_CLOSURE_TO_JS(Function function) {}
+external DART_CLOSURE_TO_JS(Function function);
 
 /**
  * Returns a raw reference to the JavaScript function which implements
  * [function].
  *
  * Warning: this is dangerous, you should probably use
  * [DART_CLOSURE_TO_JS] instead. The returned object is not a valid
  * Dart closure, does not store the isolate context or arity.
  *
  * A valid example of where this can be used is as the second argument
  * to V8's Error.captureStackTrace. See
  * https://code.google.com/p/v8/wiki/JavaScriptStackTraceApi.
  */
-RAW_DART_FUNCTION_REF(Function function) {}
+external RAW_DART_FUNCTION_REF(Function function);
 
 /**
  * Sets the current isolate to [isolate].
  */
-void JS_SET_CURRENT_ISOLATE(isolate) {}
+external void JS_SET_CURRENT_ISOLATE(isolate);
 
 /**
  * Returns the interceptor for class [type].  The interceptor is the type's
  * constructor's `prototype` property.  [type] will typically be the class, not
  * an interface, e.g. `JS_INTERCEPTOR_CONSTANT(JSInt)`, not
  * `JS_INTERCEPTOR_CONSTANT(int)`.
  */
-JS_INTERCEPTOR_CONSTANT(Type type) {}
+external JS_INTERCEPTOR_CONSTANT(Type type);
 
 /**
  * Returns the object corresponding to Namer.CURRENT_ISOLATE.
  */
-JS_CURRENT_ISOLATE() {}
+external JS_CURRENT_ISOLATE();
 
 /// Returns the JS name for [name] from the Namer.
-String JS_GET_NAME(JsGetName name) {}
+external String JS_GET_NAME(JsGetName name);
 
 /// Reads an embedded global.
 ///
 /// The [name] should be a constant defined in the `_embedded_names` library.
-JS_EMBEDDED_GLOBAL(String typeDescription, String name) {}
+external JS_EMBEDDED_GLOBAL(String typeDescription, String name);
 
 /// Instructs the compiler to execute the [builtinName] action at the call-site.
 ///
 /// The [builtin] should be a constant defined in the `_embedded_names`
 /// library.
 // Add additional optional arguments if needed. The method is treated internally
 // as a variable argument method.
-JS_BUILTIN(String typeDescription, JsBuiltin builtin,
-           [arg0, arg1, arg2, arg3, arg4, arg5, arg6,
-            arg7, arg8, arg9, arg10, arg11]) {}
+external JS_BUILTIN(String typeDescription, JsBuiltin builtin,
+                    [arg0, arg1, arg2, arg3, arg4, arg5, arg6,
+                     arg7, arg8, arg9, arg10, arg11]);
 
 /// Returns the state of a flag that is determined by the state of the compiler
 /// when the program has been analyzed.
-bool JS_GET_FLAG(String name) {}
+external bool JS_GET_FLAG(String name);
 
 /**
  * Pretend [code] is executed.  Generates no executable code.  This is used to
  * model effects at some other point in external code.  For example, the
  * following models an assignment to foo with an unknown value.
  *
  *     var foo;
  *
  *     main() {
  *       JS_EFFECT((_){ foo = _; })
@@ skipping 19 matching lines @@
 }
 
 /**
  * JavaScript string concatenation. Inputs must be Strings.  Corresponds to the
  * HStringConcat SSA instruction and may be constant-folded.
  */
 String JS_STRING_CONCAT(String a, String b) {
   // This body is unused, only here for type analysis.
   return JS('String', '# + #', a, b);
 }