Add IR printing into a supplied buffer.

vm/compiler.cc

Index: vm/compiler.cc
===================================================================
--- vm/compiler.cc	(revision 7699)
+++ vm/compiler.cc	(working copy)
@@ -187,9 +187,9 @@
       // The non-optimizing compiler compiles blocks in reverse postorder,
       // because it is a 'natural' order for the human reader of the
       // generated code.
-      intptr_t length = graph_builder.postorder_block_entries().length();
+      intptr_t length = graph_builder.postorder_block_entries()->length();
       for (intptr_t i = length - 1; i >= 0; --i) {
-        block_order.Add(graph_builder.postorder_block_entries()[i]);
+        block_order.Add((*graph_builder.postorder_block_entries())[i]);
       }
     }