dart2js: add compiler builtins to the core-runtime.

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;
 
 /**
  * Emits a JavaScript code fragment parameterized by arguments.
  *
  * Hash characters `#` in the [codeTemplate] are replaced in left-to-right order
@@ skipping 229 matching lines @@
 String JS_FUNCTION_TYPE_NAMED_PARAMETERS_TAG() {}
 
 /// Returns the JS name for [name] from the Namer.
 String JS_GET_NAME(String name) {}
 
 /// Reads an embedded global.
 ///
 /// 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) {}
 
 /**
  * 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;
@@ skipping 22 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);
 }