Redo "Use an explicit 'this' parameter instead of 'This' nodes."

pkg/compiler/lib/src/tree_ir/tree_ir_integrity.dart

 library tree_ir.integrity;
 
 import 'tree_ir_nodes.dart';
 
 /// Performs integrity checks on the tree_ir.
 ///
 /// Should only be run for debugging purposes, not in production.
 ///
 /// - Reference counts on must match the actual number of references.
 /// - Labels must be in scope when referenced.
@@ skipping 166 matching lines @@
       if (reads != variable.readCount || writes != variable.writeCount) {
         error('Invalid reference count for $variable:\n'
               '- Variable has $reads reads and $writes writes\n'
               '- Reference count is ${variable.readCount} reads and '
               '${variable.writeCount} writes');
       }
     }
   }
 
 }
-