fixed SkSL memory leak

src/sksl/SkSLParser.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
  
 #include "stdio.h"
 #include "SkSLParser.h"
 #include "SkSLToken.h"
@@ skipping 52 matching lines @@
     skslset_lineno(1, fScanner);
 
     if (false) {
         // avoid unused warning
         yyunput(0, nullptr, fScanner);
     }
 }
 
 Parser::~Parser() {
     sksl_delete_buffer(fBuffer, fScanner);
+    sksllex_destroy(fScanner);
 }
 
 /* (precision | directive | declaration)* END_OF_FILE */
 std::vector<std::unique_ptr<ASTDeclaration>> Parser::file() {
     std::vector<std::unique_ptr<ASTDeclaration>> result;
     for (;;) {
         switch (this->peek().fKind) {
             case Token::END_OF_FILE:
                 return result;
             case Token::PRECISION:
@@ skipping 1297 matching lines @@
 bool Parser::identifier(std::string* dest) {
     Token t;
     if (this->expect(Token::IDENTIFIER, "identifier", &t)) {
         *dest = t.fText; 
         return true;
     }
     return false;
 }
 
 } // namespace