Use JavaScript runtime semantics when constant folding.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index f22184e30d276639fb1c1936d6f9042114e7f6fe..69ea2b4183500a98c5ae24a0ed4be6324985eef7 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -182,14 +182,18 @@ class Compiler implements DiagnosticListener {
             this.enableTypeAssertions = false,
             this.enableUserAssertions = false,
             this.enableMinification = false,
-            bool emitJavascript = true,
+            bool emitJavaScript = true,
             bool generateSourceMap = true,
             bool cutDeclarationTypes = false])
       : libraries = new Map<String, LibraryElement>(),
         world = new World(),
         progress = new Stopwatch.start() {
     namer = new Namer(this);
-    constantHandler = new ConstantHandler(this);
+    constantHandler =
+        new ConstantHandler(this,
+                            emitJavaScript

[kasperl, 2012/09/04 05:57:30]

I would definitely compute the constant system and stuff it in a local to make
this easier to grok.

[floitsch, 2012/09/04 13:10:42]

Done.

+                            ? const JavaScriptConstantSystem()

[kasperl, 2012/09/04 05:57:30]

JAVA_SCRIPT_CONSTANT_SYSTEM?

[floitsch, 2012/09/04 13:10:42]

Done.

+                            : const DartConstantSystem());

[kasperl, 2012/09/04 05:57:30]

DART_CONSTANT_SYSTEM?

[floitsch, 2012/09/04 13:10:42]

Done.

     scanner = new ScannerTask(this);
     dietParser = new DietParserTask(this);
     parser = new ParserTask(this);
@@ -199,7 +203,7 @@ class Compiler implements DiagnosticListener {
     closureToClassMapper = new closureMapping.ClosureTask(this);
     checker = new TypeCheckerTask(this);
     typesTask = new ti.TypesTask(this);
-    backend = emitJavascript ?
+    backend = emitJavaScript ?
         new js_backend.JavaScriptBackend(this, generateSourceMap) :
         new dart_backend.DartBackend(this, cutDeclarationTypes);
     enqueuer = new EnqueueTask(this);