Fix vm code base so that it can be built for --arch=simarm (no snapshot yet).

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
===================================================================
--- runtime/vm/flow_graph.h	(revision 17160)
+++ runtime/vm/flow_graph.h	(working copy)
@@ -19,11 +19,22 @@
 class ReturnInstr;
 class ValueInliningContext;
 
-class BlockIterator : public ValueObject {
+class BlockIterator {
  public:
   explicit BlockIterator(const GrowableArray<BlockEntryInstr*>& block_order)
       : block_order_(block_order), current_(0) { }
 
+  BlockIterator(const BlockIterator& other)
+      : block_order_(other.block_order_), current_(other.current_) { }
+
+#if 0
+  BlockIterator& operator=(const BlockIterator& other) {
+    block_order_ = other.block_order_;
+    current_ = other.current_;
+    return *this;
+  }
+#endif
+
   void Advance() {
     ASSERT(!Done());
     current_++;