Fix bug when a variable is used in try/catch and accessed trough HFieldGet and HFieldSet: reference…

lib/compiler/implementation/ssa/nodes.dart

Index: lib/compiler/implementation/ssa/nodes.dart
===================================================================
--- lib/compiler/implementation/ssa/nodes.dart	(revision 7979)
+++ lib/compiler/implementation/ssa/nodes.dart	(working copy)
@@ -1215,9 +1215,11 @@
   final SourceString name;
   HFieldGet(this.name, HInstruction receiver)
       : super(<HInstruction>[receiver]);
-  HFieldGet.fromActivation(this.name) : super(<HInstruction>[]);
+  HFieldGet.fromActivation(receiver) : this(null, receiver);
 
   HInstruction get receiver() => inputs.length == 1 ? inputs[0] : null;
+  bool isFromActivation() => name === null;
+
   accept(HVisitor visitor) => visitor.visitFieldGet(this);
 
   void prepareGvn() {
@@ -1233,12 +1235,13 @@
   final SourceString name;
   HFieldSet(this.name, HInstruction receiver, HInstruction value)
       : super(<HInstruction>[receiver, value]);
-  HFieldSet.fromActivation(this.name, HInstruction value)
-      : super(<HInstruction>[value]);
+  HFieldSet.fromActivation(receiver, value)
+      : this(null, receiver, value);
 
   HInstruction get receiver() => inputs.length == 2 ? inputs[0] : null;
   HInstruction get value() => inputs.length == 2 ? inputs[1] : inputs[0];
   accept(HVisitor visitor) => visitor.visitFieldSet(this);
+  bool isFromActivation() => name === null;
 
   void prepareGvn() {
     // TODO(ngeoffray): implement more fine grain side effects.