Remove left-over compiler-code from precompiled runtime.

runtime/vm/regexp_assembler.cc

Index: runtime/vm/regexp_assembler.cc
diff --git a/runtime/vm/regexp_assembler.cc b/runtime/vm/regexp_assembler.cc
index 9e01f35101e55294e5b58cc41110d3beec891005..c916c702d8898a6ae0d82af509046cd269f60e3b 100644
--- a/runtime/vm/regexp_assembler.cc
+++ b/runtime/vm/regexp_assembler.cc
@@ -4,10 +4,23 @@
 
 #include "vm/regexp_assembler.h"
 
+#include "vm/flags.h"
 #include "vm/regexp.h"
 
 namespace dart {
 
+BlockLabel::BlockLabel()
+    : block_(NULL),
+      is_bound_(false),
+      is_linked_(false),
+      pos_(-1) {
+  if (!FLAG_interpret_irregexp) {
+    // Only needed by the compiled IR backend.
+    block_ = new JoinEntryInstr(-1, -1);
+  }
+}
+
+
 RegExpMacroAssembler::RegExpMacroAssembler(Zone* zone)
   : slow_safe_compiler_(false),
     global_mode_(NOT_GLOBAL),