Use JavaScript runtime semantics when constant folding.

lib/compiler/implementation/compiler.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.
 
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
 final bool REPORT_EXCESS_RESOLUTION = false;
@@ skipping 136 matching lines @@
   static final int PHASE_RECOMPILING = 3;
   int phase;
 
   bool compilationFailed = false;
 
   bool hasCrashed = false;
 
   Compiler([this.tracer = const Tracer(),
             this.enableTypeAssertions = false,
             this.enableUserAssertions = false,
-            bool emitJavascript = true,
+            bool emitJavaScript = true,
             validateUnparse = false,
             generateSourceMap = true])
       : 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
+                            ? const JavaScriptFoldingOperations()
+                            : const DartFoldingOperations());
     scanner = new ScannerTask(this);
     dietParser = new DietParserTask(this);
     parser = new ParserTask(this);
     patchParser = new PatchParserTask(this);
     validator = new TreeValidatorTask(this);
     resolver = new ResolverTask(this);
     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, validateUnparse);
     enqueuer = new EnqueueTask(this);
     tasks = [scanner, dietParser, parser, resolver, closureToClassMapper,
              checker, typesTask, constantHandler, enqueuer];
     tasks.addAll(backend.tasks);
   }
 
   Universe get resolverWorld() => enqueuer.resolution.universe;
   Universe get codegenWorld() => enqueuer.codegen.universe;
@@ skipping 758 matching lines @@
     final endOffset = end.charOffset + end.slowCharCount;
 
     // [begin] and [end] might be the same for the same empty token. This
     // happens for instance when scanning '$$'.
     assert(endOffset >= beginOffset);
     return f(beginOffset, endOffset);
   }
 
   String toString() => 'SourceSpan($uri, $begin, $end)';
 }