transformAsyncGeneratorBody_(tree, name) {
    tree = this.transformAny(tree);
    tree = alphaRenameThisAndArguments(this, tree);
    let statements = [];
    if (this.variableDeclarations_.length > 0) {
      statements.push(createVariableStatement(
          createVariableDeclarationList(VAR, this.variableDeclarations_)));
    }
    let body = createBlock(tree.statements);
    let createAsyncGeneratorInstance =
        this.getRuntimeExpression('createAsyncGeneratorInstance');
    statements.push(parseStatement `
        return ${createAsyncGeneratorInstance}(
            async function (${this.ctx_}) {
                ${body}
            }, ${name});`);
      return createFunctionBody(statements);
  }
@param {FunctionBody} tree
@param {IdentifierExpression} name
@return {FunctionBody}