dart2js: add compiler builtins to the core-runtime.

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

Index: sdk/lib/_internal/compiler/js_lib/foreign_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/foreign_helper.dart b/sdk/lib/_internal/compiler/js_lib/foreign_helper.dart
index 96fd0a56cba7020bec187ef598802574bc4f5b72..6b5ad3fa6cb57d17edf926ce350626d9d26d8cf8 100644
--- a/sdk/lib/_internal/compiler/js_lib/foreign_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/foreign_helper.dart
@@ -247,6 +247,16 @@ String JS_GET_NAME(String name) {}
 /// The [name] should be a constant defined in the `_embedded_names` library.
 JS_EMBEDDED_GLOBAL(String typeDescription, String name) {}
 
+/// Instructs the compiler to execute the [macroName] action at the call-site.
+///
+/// The [macroName] 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_COMPILER_MACRO(String typeDescription, String macroName,

[herhut, 2015/02/26 08:50:28]

I would prefer the macros to be typed instead of the call. If only to prevent
the getters void of any semantics like those for metadata.

+                  [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) {}