[kernel] Don't use kernel ast nodes as keys

runtime/vm/kernel.h

Index: runtime/vm/kernel.h
diff --git a/runtime/vm/kernel.h b/runtime/vm/kernel.h
index 49649aff87eb16569b83b8647a9a24ec1cc4a47f..65a681bf9e5f7d25ca6fcb057444bbb29dae0db4 100644
--- a/runtime/vm/kernel.h
+++ b/runtime/vm/kernel.h
@@ -434,9 +434,14 @@ class TreeNode : public Node {
 
   virtual void AcceptVisitor(Visitor* visitor);
   virtual void AcceptTreeVisitor(TreeVisitor* visitor) = 0;
+  intptr_t kernel_offset() { return kernel_offset_; }
 
  protected:
-  TreeNode() {}
+  TreeNode() : kernel_offset_(-1) {}
+
+  // Offset for this node in the kernel-binary. If this node has a tag the
+  // offset includes the tag. Can be -1 to indicate "unknown" or invalid offset.
+  intptr_t kernel_offset_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TreeNode);
@@ -2450,7 +2455,7 @@ class VariableDeclaration : public Statement {
   };
 
   static VariableDeclaration* ReadFrom(Reader* reader);
-  static VariableDeclaration* ReadFromImpl(Reader* reader);
+  static VariableDeclaration* ReadFromImpl(Reader* reader, bool read_tag);
 
   virtual ~VariableDeclaration();