Implement 'as' operator.

lib/compiler/implementation/ssa/variable_allocator.dart

Index: lib/compiler/implementation/ssa/variable_allocator.dart
diff --git a/lib/compiler/implementation/ssa/variable_allocator.dart b/lib/compiler/implementation/ssa/variable_allocator.dart
index d925b743af2d8c1e5804670cd91f37a6e4d999c7..3cec8c0da64857120cee5ee6f5ee90ecf6f98813 100644
--- a/lib/compiler/implementation/ssa/variable_allocator.dart
+++ b/lib/compiler/implementation/ssa/variable_allocator.dart
@@ -284,8 +284,8 @@ class SsaLiveIntervalBuilder extends HBaseVisitor {
     });
 
     env.removeLoopMarker(header);
-   
-    // Update all liveIns set to contain the liveIns of [header]. 
+
+    // Update all liveIns set to contain the liveIns of [header].
     liveInstructions.forEach((HBasicBlock block, LiveEnvironment other) {
       if (other.loopMarkers.containsKey(header)) {
         env.liveInstructions.forEach((HInstruction instruction, int id) {
@@ -556,7 +556,7 @@ class SsaVariableAllocator extends HBaseVisitor {
     }
     return true;
   }
- 
+
   /**
    * Returns whether [instruction] dies at the instruction [at].
    */