Remove old code.

lib/compiler/implementation/ssa/nodes.dart

Index: lib/compiler/implementation/ssa/nodes.dart
diff --git a/lib/compiler/implementation/ssa/nodes.dart b/lib/compiler/implementation/ssa/nodes.dart
index ac2b3e8476ea3ec39edf122906df7d7c2fc4d7a3..512fbdc98d5563f20133e0e5bc29a36466838cbd 100644
--- a/lib/compiler/implementation/ssa/nodes.dart
+++ b/lib/compiler/implementation/ssa/nodes.dart
@@ -1262,7 +1262,7 @@ class HFieldGet extends HFieldAccess {
       : super(element, <HInstruction>[receiver]);
   HFieldGet.fromActivation(receiver) : this(null, receiver);
 
-  HInstruction get receiver() => inputs.length == 1 ? inputs[0] : null;
+  HInstruction get receiver() => inputs[0];
 
   accept(HVisitor visitor) => visitor.visitFieldGet(this);
 
@@ -1282,8 +1282,8 @@ class HFieldSet extends HFieldAccess {
   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];
+  HInstruction get receiver() => inputs[0];
+  HInstruction get value() => inputs[1];
   accept(HVisitor visitor) => visitor.visitFieldSet(this);
 
   void prepareGvn() {