Make FrameStates recursive (to be used for inlining).

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index 9792a188f7d4de648074ec61e9f7742f6b1c34d4..65a46b6d020418aec6f5fb47c20a7af802590070 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -260,6 +260,12 @@ class AstGraphBuilder::Environment
   // further mutation of the environment will not affect checkpoints.
   Node* Checkpoint(BailoutId ast_id, OutputFrameStateCombine combine);
 
+ protected:
+  AstGraphBuilder* builder() const {
+    return reinterpret_cast<AstGraphBuilder*>(
+        StructuredGraphBuilder::Environment::builder());
+  }
+
  private:
   void UpdateStateValues(Node** state_values, int offset, int count);