Implement 'as' operator.

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index d8db36171f7cf84273e07f8d41bfb8ab0720bf60..c6fff5391cd2250b04bd3bbc4c4454333b4da193 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -2235,6 +2235,34 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
   }
 
   void visitTypeConversion(HTypeConversion node) {
+    Map<String, SourceString> castNames = const <SourceString> {
+      "stringTypeCheck":
+          const SourceString("stringTypeCast"),
+      "doubleTypeCheck":
+          const SourceString("doubleTypeCast"),
+      "numTypeCheck":
+          const SourceString("numTypeCast"),
+      "boolTypeCheck":
+          const SourceString("boolTypeCast"),
+      "functionTypeCheck":
+          const SourceString("functionTypeCast"),
+      "intTypeCheck":
+          const SourceString("intTypeCast"),
+      "stringSuperNativeTypeCheck":
+          const SourceString("stringSuperNativeTypeCast"),
+      "stringSuperTypeCheck":
+          const SourceString("stringSuperTypeCast"),
+      "listTypeCheck":
+          const SourceString("listTypeCast"),
+      "listSuperNativeTypeCheck":
+          const SourceString("listSuperNativeTypeCast"),
+      "listSuperTypeCheck":
+          const SourceString("listSuperTypeCast"),
+      "callTypeCheck":
+          const SourceString("callTypeCast"),
+      "propertyTypeCheck":
+          const SourceString("propertyTypeCast")
+    };
     if (node.checked) {
       Element element = node.type.computeType(compiler).element;
       world.registerIsCheck(element);
@@ -2278,6 +2306,9 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
           helper = const SourceString('propertyTypeCheck');
         }
       }
+      if (node.isCast) {
+        helper = castNames[helper.stringValue];
+      }
       Element helperElement = compiler.findHelper(helper);
       world.registerStaticUse(helperElement);
       buffer.add(compiler.namer.isolateAccess(helperElement));