Object pool with support for untagged entries.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
diff --git a/runtime/vm/assembler_arm.h b/runtime/vm/assembler_arm.h
index e8b72d92a267888018240011f1c73b43af7ce2bd..c34a940c0fbb451688753a0816e66858a60090eb 100644
--- a/runtime/vm/assembler_arm.h
+++ b/runtime/vm/assembler_arm.h
@@ -341,11 +341,9 @@ class Assembler : public ValueObject {
     return buffer_.pointer_offsets();
   }
 
-  const GrowableObjectArray& object_pool_data() const {
-    return object_pool_.data();
-  }
+  ObjectPoolHelper& object_pool() { return object_pool_; }
 
-  ObjectPool& object_pool() { return object_pool_; }
+  RawObjectPool* MakeObjectPool() { return object_pool_.MakeObjectPool(); }
 
   bool use_far_branches() const {
     return FLAG_use_far_branches || use_far_branches_;
@@ -961,7 +959,7 @@ class Assembler : public ValueObject {
 
  private:
   AssemblerBuffer buffer_;  // Contains position independent code.
-  ObjectPool object_pool_;  // Objects and patchable jump targets.
+  ObjectPoolHelper object_pool_;  // Objects and patchable jump targets.
 
   int32_t prologue_offset_;